18

Apples and Pears

Successful production of apples andpears depends in large part on good site

selection and paying meticulous attention to andfollowing through on details. The site for apple andpear orchards should be high with respect to thesurrounding area and have excellent air drainage toavoid late spring frost losses and to reduce diseasepressure. Pears are more prone to spring frost injurybecause they bloom earlier than apples. Proximity toa good water source for irrigation and spray water ishighly desirable.

Both crops perform best on deep, friable, fertile soilswith good internal drainage. Deep soils are desirablebecause of their greater water-holding capability andcapacity to continue sizing fruit under dry condi-tions. Pears will generally perform better on heaviersoils than apples. Soils that remain wet for longperiods or that have a high water table, imperviousclay pans or hardpans close to the surface, or veryheavy clay texture reduce chances of success. Wet soilspromote Phytophthora root rot, particularly in appleson susceptible rootstocks. Some of these problemscan be remedied by managing surface water throughwaterways and drainage ditches and by installingdrainage tile.

One to two years before planting, adjust the soil pH,phosphorus, potassium, calcium, magnesium, andother minor element levels as recommended.Adjustment of the soil pH to between 6.5 and 7.0and incorporation of organic matter or a greenmanure crop are highly recommended prior toestablishment. Nitrogen, applied early in the season,should be the only element required for the firstseveral years if proper soil adjustments are madeinitially. Nitrogen should be applied based on theinherent fertility of the soil and annual tree growth.Excessive nitrogen applications should be avoidedbecause they make trees more susceptible to fire

blight and reduce fruit color develop-ment and storage life. Nitrogenapplication rates are intentionally kept

low on pears to reduce fire blightsusceptibility.

Foliar nutrient applications are minimized in theMidwest because it is much cheaper and more efficientto apply fertilizers to the soil. Foliar applications aregenerally recommended to accomplish a “quick fix”when nutrient deficiencies are detected. However,calcium and boron foliar sprays are routinely appliedin many orchards. Calcium sprays are used to reducecork spot and bitter pit, since it is often difficult to getsufficient calcium into the fruit even when soil levelsare at recommended levels. Some growers also applyfoliar boron sprays annually where soil levels are low.Foliar magnesium is occasionally used where foliarsymptoms are apparent.

A combination of soil testing and leaf tissue analysis(sampled in mid- to late July) is recommended formonitoring tree nutrient levels and is used to makefertility recommendations. Consult your stateCooperative Extension Service for leaf-testingprocedures and processing instructions.

Weed pests will deprive trees of water and minerals.Although orchards will always have some weeds,noxious perennial weeds such as johnsongrass, viningmilkweed, trumpet vine, poison ivy, and yellownutsedge should be eliminated from the site prior toplanting trees.

Many midwestern growers are adopting high-densityplanting systems such as the French axis for apples.These systems use dwarf rootstocks, have consider-ably higher per acre dollar inputs, and require aconsiderably higher level of grower expertise andcultural management. However, these systems cropmuch earlier and provide a much faster return oninvestment than less dense planting systems.

C H A P T E R 1

Apples and Pears

19

Apples and Pears

Integrated Managementof Apple and Pear DiseasesThe objective of an integrated disease managementprogram is to provide a commercially acceptable levelof disease control from year to year while minimizingthe cost of disease management. For each orchard, aprogram needs to be developed that integrates allavailable control tactics.

Identifying and UnderstandingMajor Apple and Pear DiseasesAccurate disease identification is critical in makingsmart disease management decisions. Growers shoulddevelop a basic understanding of the pathogenbiology and disease life cycles for the major applediseases. The more you know about a disease, thebetter equipped you will be to make sound andeffective management decisions. The followingliterature contains colored photographs of diseasesymptoms on apples and pears, as well as informationon pathogen biology and disease development.

Compendium of Apple and Pear DiseasesPublished by the American PhytopathologicalSociety, 3340 Pilot Knob Rd., St. Paul, Minnesota55121. Phone: (612) 454-7250 or (800) 328-7560.

Diseases of Tree Fruits in the EastPublished by Michigan State University CooperativeExtension Service, as Publication NCR 45. Yourcounty Extension office may have this bulletin instock, or call Michigan State University.Phone: (517) 355-0240.

Apple ScabThe most common disease of apple in the Midwest isapple scab, caused by the fungus Venturia inaequalis.Pear scab is caused by a related fungus, Venturiapirina, but is a minor problem compared to applescab in the Midwest. Scab-resistant apple cultivars(Table 1) are recommended for growers who do notwant to use fungicides. Contact your state Coopera-tive Extension Service for information on thecultivars best suited for your region. In the moist,temperate climate of the Midwest, managingorchards where scab-susceptible cultivars are grown

Table 1. Relative resistance of apple cultivars to applediseases.

CultivarApple scab

Cedar-apple rust

Fire blight

Powdery mildew

Ben Davis 3 3 4 3Braeburn - - 4 -Cortland 4 3 3 4Delicious 3 1 2 2Early McIntosh 3 2 2 -Empire 4 2 2 3Enterprise 1 2 2 2Freedom 1 1 3 2Fuji 3 - 4 -Gala 3 - 4 -Golden Delicious 3 4 3 3Goldrush 1 4 2 2Granny Smith 3 2 4 4Idared 3 3 4 3Jerseymac 4 1 3 -Jonafree 1 3 2 2Jonagold 4 3 4 -Jonamac 3 2 3 3Jonathan 3 4 4 4Liberty 1 1 2 2Lodi 3 4 4 2Macfree 1 3 2 3McIntosh 4 1 3 3Mutsu (Crispin) 4 3 4 4Northern Spy 3 3 2 3Paulared 3 2 4 3Prima 1 3 2 2Priscilla 1 2 2 2Pristine 1 3 - 3Quinte 3 3 3 3Redfree 1 2 3 3Rome Beauty 4 4 4 3Sir Prize 1 4 4 2Smoothee 3 3 2 -Spartan 3 2 3 2Starkspur Earliblaze 3 2 3 -Stayman 4 3 2 3Tydeman’s Red 3 1 3 2Williams Pride 1 1 2 2Williams Red 3 2 2 -Winesap 4 3 2 3Yellow Transparent 3 3 4 2

Resistance rating determined in New York by Cornell UniversityExtension personnel; reports of T. van der Zwet and S. Beer,USDA Bulletin 631; D. Rosenberger, Northeast LISA AppleProject; and T. Sutton, A Grower’s Guide to Apple Insects andDiseases in the Southwest. Several cultivars have been added to thistable based on midwestern observations. Rating system; 1 = veryresistant (No chemical control needed), 2 = resistant (Chemicalcontrol needed only under high disease pressure), 3 = susceptible(Chemical control usually needed where disease is prevalent), 4 =very susceptible (Chemical control needed where disease isprevalent. These cultivars should receive first priority whencontrol is called for).

20

Apples and Pears

PRIMARY PHASE

SECONDARYPHASE

ascospores releasedduring rainy periods from green tip until about 1 - 2 weeks after petal fall

young clusters,terminal leaves, andfruit become infected

additional fruit,young leavesbecome infected

infected leavesfall to theground

secondary spores (conidia) formon surface of infected tissues

throughout spring and summer

fungus overwinters in infectedleaves on the ground

fungus formsfruiting bodies(pseudothecia)

during winter andearly spring

ascospores form withinsacs (asci) during spring;

first spores become mature atabout bud break (green tip)

wet

wetwind

Figure 2. Apple scab disease cycle.

depends on thejudicious use offungicides. Knowingthe apple scab diseasecycle (Figure 2), theweather conditions thatfavor infection (Tables 2and 3), and the basicsof how fungicides work(Table 4 and Chapter 6)will help you decidewhich fungicides to useand when to use them.

Disease Development:During winter and earlyspring, the scab fungusdevelops in fallen leavesthat were infected the previous season. The develop-ment of fruiting bodies is favored by alternating dryand wet periods. Primary scab spores (ascospores)mature in early spring about the time that leaves startto emerge. When leaves on the orchard floor havebeen wetted by at least 0.01 inches of rain for at least30 minutes, ascospores are released and carried by aircurrents to newly emerging leaves and blossoms. Themaximum rate of spore discharge is reached after 2 to3 hours of wetness; after 6 hours, 75 percent of theascospores that are mature during that wetness periodwill have been discharged. In general, maximumascospore discharge and maximum susceptibility ofleaves and fruit occur between tight cluster and 10days after petal fall. Discharge of ascospores maycontinue up to 2 weeks after petal fall, but themajority are released by first cover.

The time required for infection depends on thetemperature and duration of the “wetting period,”the period during which leaves on the tree arecontinuously wet from rain or dew (Tables 2 and 3).When the infection process is not inhibited by afungicide, primary scab lesions appear 9 to 17 daysafter infection depending on the temperature. Variousforms of the “Mills Table” (Tables 2 and 3) arevaluable for determining when conditions arefavorable for infection and for deciding whenfungicides with “after-infection” activity should beused. The Mills Table as modified by A. L. Jones inthe 1980s (Table 2) has been validated in the fieldover several years and locations. The most recentmodifications to the Mills Table (Table 3) have notbeen as widely validated but may be highly relevantto the Midwest. The newer table suggests thatinfection can happen in much less time at low

21

Apples and Pears

Table 2. Approximate minimum number of hours of leafwetting required for primary apple scab infection atvarious temperatures.a

Degree of InfectionLesion

Appearance(Days)c

AverageTemp.(˚F)

Light(hr)b

Moderate(hr)

Heavy(hr)

78 13 17 26 -77 11 14 21 -76 9 ½ 12 19 -

63 to 75 9 12 18 962 9 12 19 1061 9 13 20 1060 9½ 13 20 1159 10 13 21 1258 10 14 21 1257 10 14 22 1356 11 15 22 1355 11 16 24 1454 11½ 16 24 1453 12 17 25 1552 12 18 26 1551 13 18 27 1650 14 19 29 1649 14½ 20 30 1748 15 20 30 1747 17 23 35 1746 19 25 38 1745 20 27 41 1744 22 30 45 1743 25 34 51 1742 30 40 60 17

a From W. D. Mills, Cornell University as modified by A. L.Jones, Michigan State University.

b The infection period is considered to start at the beginning ofthe rain.

c Number of days required for lesions to appear after infectionhas been initiated.

temperatures than previous tables predicted. Forexample, according to Table 3, infection can takeplace if leaves are wet for 18 hours at 43°F, which is 7fewer hours than predicted in Table 2. Duringespecially wet springs when inoculum is high, onemight be conservative and use data from Table 3.However, Table 2 has served many growers in manyregions successfully over several years.

Within each primary scab lesion (which was causedby one ascospore), thousands of secondary spores(conidia) are produced, each of which is capable ofcausing a new infection. Conidia are spread bysplashing rain and by wind. Germination and

infection by conidia occur under about the sameconditions as for ascospores. Additional conidia areproduced all season long from established scablesions. Although fruit become more resistant as theymature, secondary infection of fruit can occur in thefall but not show up until several weeks in storage.Scab can also develop on leaves, especially their lowersurfaces, after harvest. This late-season scab may befrom new infections, from infections that occurredseveral weeks earlier, or a combination of the two. Inany case, late-season scab on leaves means that diseasepressure will be high the following spring eventhough scab was managed during the growing season.

Control of Apple Scab: The key to successful applescab control is to prevent primary infection by as-cospores. Infections by ascospores occurring prior totight cluster can cause significant losses becauseconidia are produced just as leaves and fruit reachmaximum susceptibility. If ascospores are preventedfrom establishing infections early in the season, nofurther scab control is needed after ascospores aredepleted. However, if scab is established early in theseason, a grower must fight secondary infectionsthroughout the summer. The number of conidiaproduced by just a few scab lesions is greater than thetotal number of ascospores produced in an entire acreof leaf litter in most commercial orchards.

Fungicides vary in their properties of retention,redistribution, protection, and after-infection activity(Table 4). In general, a program aimed at controllingscab will control other diseases (e.g., powdery mildewand rust) that are important early in the season.However, if you have a particular problem with otherdiseases, you may have to modify or bolster your scabcontrol program. Four general approaches to primaryscab control are:

1. Standard Protectant Program (7-day interval)Protectant fungicides must be applied at approxi-mately 7-day intervals during primary scab “season”because growing clusters and terminals are continu-ally producing new tissues that need protection. Theold rule-of-thumb is “Repeat protectant sprays after 7days of new growth or one inch of rain.” In extremelywet growing seasons, intervals of less than 7 days may berequired. Also, the less effective protectants (e.g.,

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Apples and Pears

ferbam, sulfur, thiram, and ziram) probably need tobe applied more frequently than every 7 days. Inpractice the 7-day protectant program can bemodified to take advantage of weather predictions.For example, if a protectant fungicide is used and norain is predicted on days 7, 8, and 9 after the lastapplication, the next application can be made justbefore the next rain. Unfortunately, springtimeweather throughout the Midwest is unpredictable,and a grower assumes risk in stretching spray intervalsbeyond 7 days.

2. Extended Sterol Inhibitor/Protectant Program(10-day interval not to exceed 14 days)This combination program utilizes both the protectantand after-infection activities of the different scabfungicides (Table 4 and Chapter 6) and should resultin fewer sprays than the standard protectant program.The first scab spray of the season is a protectantfungicide applied between green tip and half-inchgreen. Sterol-inhibiting (SI) fungicides are notrecommended in the first spray because there is notenough leaf tissue exposed to take up the systemicfungicide. At tight cluster, scab pressure is high, and

the first SI/protectant combination spray is made. TheSI/protectant combination provides approximately 5to 6 days of protection and 3 to 4 days of curativeactivity, which means the spray interval can beextended to 10 days. This program can also bemodified to take advantage of information oninfection periods that are determined from environ-mental monitoring (Tables 2 and 3). For example, theinterval can be extended 1 day for each day withoutinfection on days 6 through 9 after the last application.When using SI/protectant combinations, the intervalshould never exceed 14 days because some scab lesionspartially inactivated by the SI fungicides may not becompletely controlled without a second spray.

In extremely wet growing seasons, intervals of less than10 days may be required. For example, a 7- to 10-dayinterval using fungicides at their higher recom-mended rates is recommended if an infection periodoccurred greater than 2 days prior to the previous SI/protectant spray. The reasoning is as follows: The firstSI/protectant spray will reach back 3 to 4 days, butwill be most effective at halting scab development ifapplied within 2 days of an infection period. Thepurpose of the second spray is to inactivate anyfungal growth that might have survived the firstspray. Thus, the longer you wait after infection hasoccurred to apply the first spray, the more importantit is to apply the second spray after only 7 to 10 days.If the second spray is not made, then the fungus mayresume activity and produce lesions with conidia.

3. Post-infection ProgramThis program can significantly reduce the number offungicide applications, but it should be used only bygrowers who are accurately monitoring infectionperiods. It is not recommended in orchards with highlevels of scab inoculum from the previous year. Thisprogram is designed for orchards that had less than 2percent fruit scab the previous year and did not havelate-season scab on leaves. In the post-infectionprogram, an SI/protectant combination should beapplied within 72 to 96 hours after the start of aninfection period. The sooner the spray is applied afterthe infection period, the more effective it will be.Fungicides applied in a post-infection program should beused at their full recommended rates. Post-infection

Table 3. A proposed revision for the minimum number ofhours of leaf wetness required to produce apple scabinfections.a

Average temperature (˚F) Hours

34 4136 3537 3039 2841 2143 1845 1546 1348 1250 1152 9

54-56 857-59 761-75 6

77 879 11

a Data of W. MacHardy and D. Gadoury; and A. Stensvand, etal., Cornell University.

23

Apples and Pears

sprays should be followed with a second applicationof the SI/protectant 7 to 10 days later (7 is betterthan 10) to make sure that scab lesions are inacti-vated. A potential problem with this spray program isthat extended rainy periods can interfere with post-infection applications that must be made within 72to 96 hours after the start of an infection period.Indeed, extended periods of rain are a problem withany fungicide program.

4. New York IPM (Integrated Reduced Spray)ProgramThis is a minimal spray program. As is the case forthe post-infection program, it is not recommended inorchards that had greater than 2 percent fruit scab theprevious year or late-season scab on leaves. The firstfungicide application is delayed 1 to 3 weeks; a totalof four applications of an SI fungicide (e.g.,fenarimol, myclobutanil) is made: 1) tight cluster(with oil); 2) pink (with insecticide); 3) petal fall(with insecticide); and 4) first cover (with insecti-cide). Optimal protection is achieved by mixing aprotectant (e.g., captan, mancozeb, or metiram) with

the SI fungicide, especially at petal fall and first coverwhen young fruit are highly susceptible to infection.Including a protectant with the SI should also delaydevelopment of resistance to the SI. Because this is aminimal spray program, spray coverage must benearly perfect. Thus, the program is not suited toblocks of large trees where near-perfect coverage isimpossible. The timing of the four applications isdictated by the weather (spraying when conditionswill allow optimal coverage) and timing of insect andmite control rather than by infection periods.However, if intervals greater than 10 days occur (e.g.,from pink until petal fall), and weather conditionshave been favorable for infection, it may be necessaryto compensate by increasing the sterol inhibitor tothe highest rate permitted on the product label.

Monitoring for Scab: Losses from scab often occurwhen conidia, formed in primary infections, infectyoung, developing fruit. Therefore, orchard blocksshould be monitored for scab lesions starting at petalfall and continuing through first cover. Examine bothsurfaces of spur leaves and fruit. If scab is detected, the

Table 4. Properties of fungicides for apple scab control.

Trade NamesaCommon

NamesRate/100gallons Retentionb Redistributionc

After-infectionactivityd (hr) Protectione

Benlate 50WP benomyl 3.0 oz Good Good 18-24 FairCaptan 50WP captan 2.0 lb Good Good 18-24 Very GoodCarbamate 76WP ferbam 2.0 lb Good Good None GoodDithane M-45 80WP mancozeb 2.0 lb Good Good 18-24 Very GoodManzate 200 80WP mancozeb 2.0 lb Good Good 18-24 Very GoodNova 40% WP myclobutanil 2.0 oz Fair Fair 72-96 FairPenncozeb mancozeb 2.0 lb Good Good 18-24 Very GoodPolyram 80WP metiram 2.0 lb Good Good 18-24 Very GoodProcure 50WS triflumizole 4.0 oz - - 48-72 -Rubigan 1E fenarimol 3.0 fl oz Poor Poor 72-96 FairSulfur 95% sulfur 5.0 lb Fair Good None FairSyllit 65WP dodine 0.5 lb Good Good 30-36 Very GoodThiram 65% WP thiram 2.0 lb Fair Fair 15-20 FairTopsin-M 70WP thiophanate-

methyl3.0 oz Good Good 18-24 Fair

Ziram 76DF ziram 2.0 lb Good Good 18-24 Gooda No discrimination or endorsement is implied by the Cooperative Extension Service. Not a complete list. Also see Chapter 6 of this

handbook for information on attributes of different fungicides.b Retention is the ability of the fungicide to stick to the leaf surface.c Redistribution is the ability of a fungicide to move to unsprayed areas and onto new growth during rains and weathering.d After-infection activity is the ability to inhibit infection that has started. Use the start of a rain as the start of infection. At average

temperatures below 50˚F, use the longer time; at average temperatures above 50˚F, use the shorter time.e Protection is the ability of a fungicide to protect tissue from new infections after the material is applied.

24

Apples and Pears

safest recommendation is to apply an SI at the fullrecommended rate plus a protectant through secondcover to suppress further development of lesions and toprotect susceptible fruit. In orchards where dodine hasnot been used extensively, and therefore resistance tododine is unlikely, this fungicide may help “burn out”existing lesions. However, dodine applied after bloomcan cause russeting. Another option is to not make“burning out” lesions the primary goal, but rather tofocus on protecting fruit with the full rate of captan oran EBDC fungicide (e.g., mancozeb, maneb, ormetiram). Note that after pre-bloom, the EBDCs maynot be used at rates greater than 3 lb per acre.

Powdery MildewPowdery mildew, caused by the fungus Podosphaeraleucotricha, can seriously reduce the vigor and produc-tivity of apple trees. Powdery mildew is usually not assevere a problem as scab in the Midwest, but on highlysusceptible varieties (Table 1) the mildew fungus maydeform, stunt, or kill twigs, leaves, blossoms, and fruit.Infected fruits may become severely russeted. Gray towhite felt-like patches occur on the leaves and on 1-year-old twigs. Leaves are narrow, crinkled, and foldedlengthwise, and they become thickened.

Disease Development: The powdery mildew fungusoverwinters in vegetative or fruit buds infected theprevious season (Figure 3). Infected terminals mayhave a silvery gray color, stunted growth, and amisshapen appearance and are more susceptible towinter injury than are noninfected terminals.Temperatures near –18°F kill a majority of mildew-infected buds and the fungus within them. Thus,disease pressure from powdery mildew is usuallygreater in growing seasons following mild winters.

As buds break dormancy, the powdery mildew fungusresumes growth and colonizes developing shoots,causing primary infections. Primary mildew infec-tions may occur on vegetative shoots and blossomsand thereby cause a reduction in yield. The powderywhite appearance on infected shoots consists of manythousands of spores, which are responsible forsecondary infections. Secondary infections usuallydevelop on leaves and buds prior to terminal bud setin midsummer and may reduce the vigor of the tree.

Young fruit may become infected from about thepink stage of flower bud development up to 1 to 3weeks after bloom. Fruit infection results in a weblikerusseting on the mature fruit. Infected buds are theprimary means of overwintering for the fungus. Thepowdery mildew fungus produces masses of smallblack fruiting bodies called cleistothecia on infectedleaves and terminals in the late summer and fall.Although cleistothecia contain ascospores, their rolein the disease cycle is not clearly understood.

The conditions required for infection by the powderymildew fungus are very different from those requiredby the scab fungus. Unlike the apple scab fungus, thepowdery mildew fungus does not require leaf wetnessfor infection. In fact, powdery mildew spores will notgerminate if immersed in water. Rather, powderymildew infections occur when the relative humidity isgreater than 90 percent and the temperature is between50° and 77°F. The optimal temperature range for thefungus is 66° to 72°F. The high relative humidity thatoften occurs before and after wetting periods isconducive to powdery mildew development. Underoptimal conditions, powdery mildew will be obviousto the naked eye 48 hours after infection. About 5 daysafter infection, a new crop of spores is produced. Non-germinated powdery mildew spores can tolerate hot,dry conditions and may persist in the orchard untilconditions are favorable for germination and infection.

Control of Powdery Mildew: Apple cultivars vary inrelative resistance to powdery mildew (Table 1).Because powdery mildew does not need a wettingperiod to develop, control measures may be neededeven during dry weather. The critical period forpowdery mildew control is from about tight clusterto pink through first or second cover. The SI fungi-cides that are used to control apple scab (e.g., Nova,Procure, and Rubigan) are also effective againstpowdery mildew. Another SI fungicide, Bayleton(triadimefon), is a good mildewcide but is lesseffective in controlling scab. Wettable sulfur (95%WP) is a good mildewcide but is relatively weakagainst scab and can be phytotoxic at temperaturesgreater than 80°F. Thorough spray coverage, includ-ing the tops of trees, is essential for control ofpowdery mildew with fungicides.

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Apples and Pears

Rust DiseasesThree rust diseases commonly infect apples in theMidwest: cedar-apple rust (Gymnosporangiumjuniperi-virginianae), quince rust (G. clavipes), andhawthorn rust (G. globosum). Pears are susceptible toquince rust and hawthorn rust but not to cedar-applerust. All three rust fungi require infection of easternred cedar or related species of Juniperus to completetheir life cycles. The rust diseases are usually kept incheck by fungicides aimed at scab. Where fungicideuse is minimal (e.g., on scab-resistant cultivars or inorganic orchards), rust diseases, especially cedar-applerust, can severely spot leaves and mar fruit. Quincerust causes fruit lesions but rarely affects leaves ofapple. Hawthorn rust causes leaf lesions but rarelyaffects apple fruit.

Cedar-apple rust leaf spots initially develop on theupper leaf surfaces shortly after bloom. Lesions arepale yellow, but as they expand, they turn orange,which distinguishes them from other types of leafspots. Later, small black dots (fungal fruiting

structures called pycnia) appear in the orange rustspots. By late summer, tiny fungal tubes (aecia)emerge from the lower leaf surfaces. Extensive leafinfection may cause early defoliation, which in turnweakens the tree.

Fruit infection by cedar-apple rust is most commonnear the blossom end. The yellowish orange lesionsare similar to but much larger than those on leaves.The lesions have a dark green border and are up to1/16-inch deep; the tissue beneath the lesions isunaffected. Quince rust lesions on fruit are darkgreen, 3/4 to 1 1/2 inches in diameter, and becomepuckered at the blossom end. The tissue beneath thelesions is brown and spongy, and necrosis can extendto the core.

Disease Development: The disease cycles of the threerust fungi are similar and relatively complex. Cedar-apple rust involves two hosts, three types of fruitingstructures (telia, pycnia, and aecia), and requires 2years to complete its disease cycle (Figure 4). Thefungus overwinters in reddish brown galls on cedar

infected

dormantterminal

fungus overwintersin diseased buds

disease is apparent onshoots and leaves as

they emerge in the spring

silver tip

infectedterminal

infectedblossoms

spores areproduced and thendispersed by wind

infection of leaves,shoots, and fruits

cleistothecia (fruiting bodies)develop on leaves and shoots

developing budsbecome infected

humidity

PRIM

ARYM

ILDEW

SECONDARYMILDEW

Figure 3.Powdery mildewdisease cycle.

26

Apples and Pears

basidiospores

windbornebasidiospores

infect young fruitand leaves

pycnium on upperleaf surfacein early summer

aecium on lowerleaf surfacein late summer

aeciospores are windborneand infect cedar leaves or budsin late summer

galls on cedar twigsdevelop and mature

over two seasons

orange, gelatinoustelial horns extrude from

galls with spring rains

red cedar

cross-sectionof infected leaf

a telial horn bearingmasses of teliospores

teliospores

germinating teliosporeson telial horn

Figure 4. Cedar-applerust disease cycle.

trees. When wet in the spring, orange, gelatinoustendrils, or “horns,” containing teliospores emerge.The teliospores germinate to form basidiosporeswhich are carried by wind to apple trees. Basid-iospores germinate if temperature and wettingrequirements have been met (Table 5). No infectionoccurs below 43°F because basidiospores are notproduced. Fruit are most susceptible for 2 to 3 weeksstarting at bloom; leaves are most susceptible when 4to 8 days old. Once release of basidiospores fromcedar trees has ceased (generally by second or thirdcover), there is no further infection of apple tissues.Unlike apple scab, cedar-apple rust lesions on appleleaves will not produce spores that reinfect appleleaves and fruit. Instead, fungal mating occurs in rustlesions which result in the formation of aecia. Aeciarelease aeciospores which are carried by wind to cedartrees where they infect and complete the disease cycle.Galls start to develop on cedar shortly after infectionbut do not exude telial horns until the second springafter infection.

Control of Rust Diseases: Some apple cultivars areresistant to cedar-apple rust (Table 1). Removingcedars within a 2-mile radius of an orchard will disruptthe disease cycle, and fungicides may not be needed.Many of the fungicides directed at scab will alsocontrol rust, although captan, dodine, and benomyl donot control rust diseases. The basidiospores that infectapples are produced and released from cedar gallsstarting at about the pink stage of flower bud develop-ment through first or second cover; this is the mostcritical time for control with fungicides.

Fire BlightFire blight, caused by the bacterium Erwiniaamylovora, is a serious disease of apples, pears, andrelated ornamental plants. Incidence and severity areinfluenced by cultivar and rootstock susceptibility(Tables 1 and 6), the weather, and the amount ofsucculent tissue present. Managing fire blight requiresan integrated approach that relies primarily on

27

Apples and Pears

cultural practices and is supported by the judicioususe of bactericides.

Disease Development: The fire blight bacteriumoverwinters in cankers on branches and trunks(Figure 5). In the spring, bacteria-laden ooze isexuded from the canker margins. Splashing rain andinsects carry the pathogen to blossoms, and beesfurther spread the pathogen as they pollinate. If theweather is warm and rainy or humid, populations ofE. amylovora double every few hours, and more thana million bacterial cells can colonize a single floralstigma. Rain or dew then washes the bacteria intoopenings at the base of the blossom. The pathogencan apparently move systemically within the plant toshoot tips and rootstocks. This may explain why treessometimes are severely damaged or killed by shootand rootstock infections even when blossom infectionwas minimal or absent. Sudden or “explosive”outbreaks of fire blight often appear about 1 to 2weeks following a storm with strong winds or hailthat damage succulent tissue. Apparently severalsimultaneous inoculations occur during the storm,and bacteria multiply rapidly in succulent shoots; this

Table 5. Approximate minimum number of hours of leafwetness required for cedar-apple rust infections on leavesof susceptible cultivars.

Degree of Infectiona

Average Temperature (˚F)

Light(Hours)

Heavy(Hours)

36 24 -40 12 2443 8 1046 6 750 5 654 4 558 3 561 3 464 3 4

68 to 76 2 479+ - -

a Based on the data of Aldwinckle, Pearson, and Seem, CornellUniversity. Assumes that cedar-apple rust inoculum (orange,swollen galls bearing teliospores with basidiospores on cedartrees) is available at the start of the rain. If inoculum is notalready present (dry period prior to the rain), add 4 hours attemperatures above 50˚F and 6 hours at temperatures of 46˚ to50˚F. Infection is unlikely at temperatures below 43˚F ifinoculum is not already present.

Table 6. Relative resistance of apple rootstocks, pearvarieties, and pear rootstocks to fire blight.Apple Rootstocks

ResistantModeratelyresistant Susceptible

Geneva 11 Bemali AlnarpGeneva 30 Bud.118 Bud.9Geneva 65 Bud.490 M.9M.7 MM.106 M.26Novole MM.111 M.27Robusta 5 Mark

Ottawa 3P.2P.16P.22

Pear and Asian Pear Varieties

ResistantModeratelyresistant Susceptible

Ayers Dawn AuroraHarrow Delight Douglas BartlettHarrow Sweet Garber BoscHoneysweet Harvest Queen Clapp’s FavoriteKieffer Lincoln d’AnjouMagness Luscious DeVoeMaxine Rogue Red EarlibriteMonterey Seckel Flemish BeautyMoonglow Spartlett HighlandPotomac Worden Seckel SierraTyson Chojuro Starkrimson

Shinseiki (NewCentury)

Hosui

Nijisseiki (20thCentury)

Pear and Asian Pear Rootstocks

ResistantModeratelyresistant Susceptible

Old Home (OH) P. betulaefoliaseedlings

Bartlett seedlings

OH x Farmingdale(OHF)(except OHF 51)

Provence quince

P. calleryana Winter Nelisseedlings

Adapted from Fire Blight–Its Nature, Prevention, and Control byT. van der Zwet and S. V. Beer, USDA Agriculture InformationBulletin No. 631.

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Apples and Pears

rain washes bacteria tonatural openings at flower

base; infection occurs

flower clusterbecomes blighted

bacteria are spreadfrom blighted clusters

to young growingshoots; infection occurs

through wounds

repeated infections of succulentshoots occur through wounds,

as bacteria are spread byinsects and rain

susceptible rootstock suckersbecome infected; infection

expands and causes rootstockcanker, killing the tree

bacteria from blighted shootsmove systemically within the

tree; cause blight of susceptiblerootstock or interstem,

killing the tree

infections expand from succulentshoots into supporting wood,

causing cankers

bacteriaoverwinterin cankers

overwintering bacteria multiply,move through wood to nearbyshoots, causing them to blight

bacteria-ladenooze at canker

margins

insects attracted toooze, transfer bacteria

to flower stigmas

bees transfer bacteriato additional flowers;

bacteria multiply on stigmasat temperatures above 65˚F

rain

insects

late sprin

g

insects, rain

insects, rain

earl

y sp

ring

Figure 5. Fire blight disease cycle.

leads to the sudden appearance of symptomsthroughout a block of trees.

Control of Fire Blight: Methods for consistent andreliable control of fire blight are not available.Relatively resistant cultivars and rootstocks (Tables 1and 6) should be planted whenever possible. Highlysusceptible combinations (e.g., Gala on M.26) shouldbe avoided. Fertilization, especially nitrogen applica-tion, should be adequate for tree health withoutpromoting rapid growth and prolonged succulence.Susceptible varieties should be pruned to improvetree shape and promote rapid drying of foliage butshould not be pruned aggressively.

Pruning fire blight strikes during the growing seasonis a controversial issue. Removing sources of thepathogen is desirable, but pruning can actually make

fire blight worse by increasing the amount ofsucculent tissue and by spreading the pathogen ontools. If fire blight strikes are so numerous that is notpractical to remove them all, then wait until thedormant season. If fire blight strikes are few, it maybe practical to remove them. They should be removedby making cuts at least 12 inches below visiblesymptoms. The computer program MARYBLYT,available from pest management suppliers (seeAppendix B), is useful for predicting the onset ofsymptoms. With this knowledge, growers with smalltrees and adequate labor can scout for and remove thefirst infected tissues before symptoms becomewidespread. This will not eliminate further symptomsbut may reduce the spread of fire blight. Missedstrikes and cankers should be pruned during thedormant season.

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Apples and Pears

Chemical control of fire blight is effective during thespring when the pathogen is at the surface of cankersand on flowers. After the bacterium has invadedtissues, it is beyond the reach of chemicals. Sprays ofcopper sulfate when cankers are active but beforeleaves have emerged, and fixed copper at 1/4-inchgreen tip, may reduce populations of the fire blightbacterium. Be aware, however, that if little rain (lessthan 2 inches) falls between an early copper applica-tion and petal fall, the copper residues could be greatenough to damage fruit finish.

Streptomycin applied during bloom will reduceblossom infections unless streptomycin-resistantstrains of E. amylovora are present. The MARYBLYTprogram is useful for accurately timing streptomycinapplications. Without information fromMARYBLYT, applications should be made every 3 to4 days during bloom if the average temperature is65°F or greater and there is rain or relative humidityof 60 percent or greater. Streptomycin works bestwhen not tank-mixed with fungicides and whenapplied at night or when drying conditions are slow.Streptomycin applications made after bloom aregenerally ineffective at controlling shoot infections.The number of streptomycin applications should bekept to a minimum to reduce the risk of selectingstreptomycin-resistant strains of the pathogen.Streptomycin resistance is a serious problem incommercial orchards in southwestern Michigan, partsof Missouri, and the western states.

Collar and Crown RotRoot, crown, and collar rot, caused by the soil-bornefungus Phytophthora cactorum and other species ofPhytophthora, is a perennial problem in midwesternapple orchards. Phytophthora belongs to a group offungi known as the “water molds” because water iscritical for many stages of its life cycle. AlthoughPhytophthora species are common in agricultural soils,disease is most frequently found in areas with heavy,poorly drained soil and is especially severe onMM.106 and M.26 rootstocks. The pathogen attacksthe lower trunk just at or below the soil surface.Cankers may extend up the trunk to the rootstock-scion union or beyond if the scion is susceptible toPhytophthora. Cankers at the base of the tree have

dark, sunken bark; infected tissue beneath the barkappears reddish brown to dark brown. Leaves onaffected trees may be small and pale during thesummer and turn reddish in late summer. Withrelatively recent infections, a sharp line often delimitshealthy from infected tissue. However, Phytophthorarots are easily confused with fire blight infections ofrootstocks. Distinguishing the two diseases requiresevaluation of host susceptibility, site conditions,disease history, and often culturing of the pathogen(s)from infected tissue in the laboratory.

Control of Collar and Crown Rot: Good watermanagement and site selection are the most importantfactors for control of Phytophthora diseases. Orchardsoils should be well drained and leveled before planting.For trees that are already planted, drainage should beimproved in the vicinity of the trunk, making surewater is not allowed to pool around the base of thetrunk. If subsurface drainage is a problem, the onlysolution may be to install drainage tile—a task moreeasily done before trees are planted. Relatively resistantrootstocks include M.9, Mark, Bud.118, and Bud.9.However, some of these rootstocks are highly suscep-tible to fire blight (Table 6).

In areas of orchards historically affected by root,crown, or collar rot, fungicides may be needed tominimize damage. Fungicides will not be effective ifthe cultural practices discussed above are not fol-lowed, and they will not revitalize trees showingmoderate to severe rot symptoms. See the currentCommercial Tree Fruit Spray Guide and the productlabel for details on using fungicides to manage root,crown, and collar rot.

Summer DiseasesBitter rot, black rot, and white rot (bot rot) are themost common summer rot diseases of apple. Flyspeckand sooty blotch cause superficial blemishes whichdetract from the appearance of apple and pear fruit.The summer diseases have the potential to causeserious losses, especially in the more southern regionsof the Midwest and on trees not sprayed withfungicides. In the northern regions of the midwest,some fruit rot fungi invade winter-injured tissue andare associated with branch cankers. Any condition

30

Apples and Pears

that reduces tree vigor will increase susceptibility tobranch and trunk infections. Flyspeck and sootyblotch fungi, and some of the fruit rot fungi, surviveon a wide range of woody plants. The fruit rot fungiare similar in many respects:• they survive in dead or weakened tissue, including

fire blight cankers and mummified fruit;• they produce enormous numbers of spores which

are readily disseminated by rain and wind; and• the diseases they cause are favored by warm,

humid weather.

Bitter RotSymptoms vary slightly, depending on which sporetype (ascospore of Glomerella cingulata or conidiumof Colletotrichum gloeosporioides or C. acutatum)causes the infection. Lesions incited by conidia aresunken, light brown, and often marked with concen-tric circles of spore masses that appear creamy andsalmon- to pink-colored under humid conditions.Lesions incited by ascospores are usually not sunkenand are darker than those caused by conidia. Spore-producing bodies are scattered over the lesion in darkbrown to black clusters. Bitter rot decay extends in acone shape toward the core, which helps distinguishbitter rot from other fruit rots. The rotten spots aresoft but firmer than white rot lesions.

Black RotIn addition to affecting fruit, the black rot fungus,Botryosphaeria obtusa, causes leaf spots (frog-eye leafspot) and branch cankers. The optimal temperaturefor fruit infection is 68° to 75°F with 9 hours ofwetting. Fruit symptoms often start at the blossomend. Dark brown lesions expand and eventually canencompass the entire fruit. Lesions are often markedby concentric alternating brown and black rings. Therotted area is firm, leathery, and dotted with darkfungal fruiting bodies. Fruit infection can occurthroughout the growing season; however, rotsymptoms generally appear as fruit reach maturity.

The optimal temperature for leaf infection is 80°Fwith 4 1/2 hours of wetting. Leaf spots first appearabout 1 to 3 weeks after petal fall as purple flecks thatexpand to about 1/4-inch in diameter. The margins

of spots remain purple, while the centers turn tan tobrown so that the spots resemble a “frog’s eye.” Spotscan enlarge and become irregular in shape as they areinvaded by other fungi later in the season. The leafspot phase is not economically important unless itresults in significant defoliation.

Branch cankers initially appear as slightly sunkenreddish brown areas on the bark. Fire blight cankersand winter-injured tissue are frequent sites for blackrot canker initiation. Cankers can expand to severalfeet in length and girdle limbs. Branches are weak-ened and sometimes killed.

White Rot (Bot Rot)White rot (Botryosphaeria dothidea) lesions begin onfruit as small, circular, tan spots that are sometimessurrounded by a red halo. Duchess, Golden Deli-cious, Grimes Golden, Gallia Beauty, Rome, andYellow Transparent varieties are all highly susceptibleto white rot. Jonathan and Red Delicious aregenerally less affected. The rot extends in a cylindricalshape toward and surrounding the core. Eventuallythe entire fruit becomes soft, watery, and light tan.Under cooler conditions the rot may be darker andclosely resemble black rot. Branch infections start outas reddish brown bark lesions that expand andsometimes exude fluid. Cankers are more severe iftrees are stressed by drought.

Flyspeck and Sooty BlotchFlyspeck and sooty blotch are two separate diseasesthat frequently occur together on the same fruit.Flyspeck appears as clusters of tiny, black dots. Sootyblotch appears as dark, sooty smudges. The fungi thatcause flyspeck (Zygophiala jamaicensis) and sootyblotch (Peltaster fructicola, Gastrumia polystigmatis,Leptodontium elatius, and others) overwinter on thetwigs of many woody plants, especially brambles.Spores of sooty blotch fungi are spread during rain.The flyspeck fungus is spread as airborne ascosporeswhich are released during rain or as airborne orwaterborne conidia. Fruit infection can occur anytime after petal fall but is most prevalent during mid-to late summer. Both diseases are favored by tempera-tures between 65° to 80°F and by high relative

31

Apples and Pears

humidity at the fruit surface (greater than 90 percentfor sooty blotch and greater than 95 percent forflyspeck). Conditions such as these are most frequentwhen nighttime temperatures remain near 65° to70°F or during extended warm rainy periods. Thediseases flourish in orchards subject to heavy dews orfog. Under ideal conditions, sooty blotch andflyspeck symptoms can develop within 14 days ofinfection, but symptom development is arrested byhigh temperatures and low relative humidity. Thus,the period between infection and symptom develop-ment ranges from 25 to more than 60 days in theNortheast and may be similar in the Midwest. Sootyblotch and flyspeck infections not yet visible atharvest can develop during storage.

Control of Summer DiseasesA combination of annual pruning, adequate fruitthinning, orchard sanitation, and protective fungi-cides is the key to controlling summer diseases.

Pruning and Thinning: Pruning systems that openthe tree canopy to light should also improve airmovement and thereby reduce relative humidity andthe time that leaves and fruit are wet. For example,summer pruning, as opposed to dormant pruning,reduced the incidence of flyspeck on apple fruit by 50percent in research conducted in Massachusetts.Keeping the orchard mowed should also promote airmovement, enhance rapid drying, and in turn, reducesummer diseases. Thinning of fruit is important toimprove spray coverage and drying. Clustered fruitoften have flyspeck on their inner faces even when anadequate fungicide program has been used.

Sanitation: Dead or weakened wood in or near anorchard can serve as a reservoir for the fungi thatcause summer diseases. Therefore, removal anddestruction of dead and dying plant material,including the current year’s fire blight strikes, isnecessary to keep the level of summer disease fungi toa minimum. Removing unwanted vegetation thatmight be a reservoir for pathogens, particularly wildbrambles, should also reduce disease pressure in theorchard.

Fungicides: Different fungicides are recommendedfor the different summer diseases. In general,protectant fungicides (e.g., captan, ziram) that arepermitted later in the season are used alone or mixedwith benomyl (Benlate) or thiophanate-methyl(Topsin-M). See the current Commercial Tree FruitSpray Guide for specific recommendations.

Insect and Mite Pestsof Apples and PearsControl of the major insect pests of apples incommercial production involves timely insecticideapplications. Unlike some crop pests, pests of applescan be very elusive, and damage can often occurwithout individual pests being seen. To maintainhealthy, productive trees and fruit, producers shouldrecognize what pests to look for, understand pestbiology, use appropriate preventive measures, andapply timely controls when needed.

Identifying and UnderstandingMajor Apple and Pear PestsIt is important for growers to recognize all stages ofthe insects and mites that attack apples and pears.Proper identification is critical to making the correctmanagement decisions. In addition, growers shoulddevelop a basic understanding of the pest. The moreyou know about the pest, the better equipped youwill be to make sound and effective managementdecisions. The following literature contains colorphotographs of pests of apples and pears, as well asinformation on their biology.

Common Tree Fruit PestsAuthored by Angus Howitt and published as NorthCentral Regional Extension Publication #63 byMichigan State University Cooperative ExtensionService. Phone: (517) 355-0240.

Mid-Atlantic Orchard Monitoring GuideEdited by Henry Hogmire and published as NRAES75 by the Northeast Region Agricultural EngineeringService, Cooperative Extension Service.Phone: (607) 255-7654.

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Apples and Pears

Codling Moth(Cydia pomonella; order Lepidoptera, family Tortricidae)

Damage: Codling moth is a serious pest of applesand pears. Larvae damage apples and pears bychewing their way into the center of the fruit.“Frass,” or fecal material, is pushed out through theside of the fruit skin or the calyx end. Wounds causedby codling moth larvae promote the development offruit rots. Most of the damage is caused by second-and third-generation larvae.

Appearance: The adult moth is about 3/8-inch longand blends in well with the bark. The adult moth’sforewings are gray-brown crossed with light gray andwhite lines and with deep gold or bronze wing tips.The larva is white, often tinged with pink, and has abrown head.

Life Cycle and Habits: The fullydeveloped larva is the overwintering

stage. Pupation occurs in spring beginningabout the same time as bloom, with adults first

active in late April or early May. Female moths laythe scale-like eggs singly on developing fruit oradjacent leaves or stems just after sundown eachnight. Upon hatching, the larva enters into the calyxend or side of the fruit, then tunnels to the centerwhere it feeds and develops. Brown frass is oftennoticed near the calyx end of the developing fruit.Larval development is completed in 3 to 5 weeks.Larvae exit the fruit to pupate in a thick silkencocoon on the bark or other protected areas. In theMidwest, there are two generations and sometimes apartial third one.

Monitoring and Thresholds: Management of codlingmoth in commercial orchards relies on regularexamination of the fruit, pheromone trapping, and theuse of degree-day models. Pheromone traps for thispest need to be monitored from pink through harvest.Typically, the first moth catch is at bloom, and two orthree generations should be expected throughout theyear. Traps help determine timing of sprays; spraysshould target larvae emerging from eggs.

The biofix for the codling moth is the starting date ofthe first sustained flight of male moths captured inpheromone traps. Generally, this is when the fifth

moth has been captured in the trap. A few moths oftenemerge very early in the spring ahead of the rest. Usingthe fifth moth as the biofix better represents when themajority of the codling moths begin to emerge. Thisusually occurs just after petal fall. Sprays should beapplied when 250 degree-days (50°F threshold) haveaccumulated after the cumulative capture of five mothsper trap. Typically, 1,000 degree-days are needed tocomplete each generation. Growers should use anaction threshold of an average of five or more mothsper week throughout the season. An insecticideapplication should be made 250 degree-days later if thenumber of moths exceed this threshold.

For one season, a grower will need a minimum of twowing traps (two plastic trap tops, two wire hangers),ten to 25 wing trap bottoms (sticky cardboard), andten pheromone lures. Hang codling moth pheromonetraps in the southeast quadrant of the tree, 6 feet offthe ground. Avoid hanging traps in outside rows.

Mating Disruption: Isomate C-plus and CheckMateCM are registered for the control of codling moth.They dispense the sex attractant of the codling mothand are designed to prevent male moths fromlocating females for mating. This strategy, termedmating disruption, is most likely to succeed in blocksof at least 5 acres and where initial populations ofcodling moth are low. If mating disruption is used forcodling moth control in smaller blocks, or whereinfestations are greater, border sprays or at least oneor two cover sprays will also be necessary. Controllingcodling moth by mating disruption will not controlother insect pests that are controlled by cover sprays(plum curculio and apple maggots, for example).Isomate C-plus has performed better thanCheckMate CM in most studies.

Chemical Control: Control of codling moth later inthe season is assisted by good control of the firstgeneration.

Plum Curculio(Conotrachelus nenuphar; order Coleoptera, familyCurculionidae)

Damage: Plum curculio attacks apples and pears.Surface feeding and egg laying by overwinteringadults can scar or misshape the fruit by harvest, and

codling moth

33

Apples and Pears

feeding by larvae may cause somepremature fruit drop. Newlyemerging adults in the summer

feed on apples for a short time, causing round feedingscars that penetrate the fruit about 1/4-inch.

Appearance: The adult is a typical snout beetle,1/4-inch long, dark brown with patches of white orgray. There are four prominent humps on the wingcovers. The snout is one-quarter the length of thebody, with mouth parts located at the end. The larvais a legless, grayish white grub with a brown head. Itslength is about 1/3-inch when fully grown.

Life Cycle and Habits: Plum curculio overwinters asadults in ground litter or soil, usually outside theorchard. Adults migrate into the orchards eachspring. Typically, the first signs of damage coincidewith the onset of 60°F nighttime tempera-tures. Eggs are laid on crescent-shapedflaps cut in the skin of young fruit.Often border rows near woods are thefirst to show injury. Apples andpears attacked by plum curculiowill drop from the tree early in theseason, along with poorly pollinated fruit. Whenlarvae are fully developed, they leave the fruit, dropto the ground, and pupate 1 to 2 inches below thesurface. Adults emerge in midsummer and may feedon the fruit before leaving the orchard to findoverwintering sites. There is one generation per year.

Monitoring and Thresholds: Currently there are nomethods to accurately predict when plum curculiodamage will occur. However, plum curculio pyramidtraps are currently being tested in several midwesternstates.

Chemical Control: Plum curculio is usually con-trolled with petal-fall and first-cover insecticide spraysdirected at the adult before egg laying. Considerableegg-laying damage can occur over a short period oftime. Where plum curculio has been a problem in thepast, use preventive sprays at petal fall and first coverto reduce damage. Cool weather during petal fall maydelay the immigration of the adults into the orchard.Under these conditions, a first-cover and possibly asecond-cover spray may be needed to control plumcurculio.

Apple Maggot(Rhagoletis pomonella; order Diptera, family Tephritidae)

Damage: Apple maggot mainly attacks apples. Eggpunctures and larval feeding cause fruit to bedimpled, and if it is soft, the fruit will soon rot.

Appearance: Adult apple maggot flies have darkbands on their wings and white bands around theabdomen. There is a large white spot on the thorax.The larva, when fully grown, is about 1/3-inch long,cream colored, and legless.

Life Cycle and Habits: Apple maggot passes winter asa pupa, and adults emerge from June to September,with most adults emerging in June and July. Theypuncture the skin of an apple and insert an egg intoit. The maggots hatch and feed by tunneling through-out the apple flesh, leaving tiny brown trails. Applemaggots are common in northern Illinois, Indiana,and Ohio and absent in the southern parts of thesestates. They seldom cause damage south of U.S.Highway 40. There is one generation per year (maybetwo in southern range). Check with local Extensionpersonnel for apple maggot incidence in your area.

Monitoring and Thresholds: Traps are used tomonitor for apple maggot flies from early Junethrough mid-August. Use yellow sticky traps or redspheres baited with fruit volatile lures. Place alongedges of blocks nearest an abandoned orchard orwoodlot; if these are not present, then along thesouthern edge of blocks. If traps are not used in everyblock, put them in the earliest-maturing variety orblocks closest to abandoned orchards. Place the trapin the outer part of the midcanopy (eye-height) of thetree in a relatively exposed spot; prune back anyclusters or shoots within 6 to 12 inches of the trap.

Compare the appearance of the trapped flies withpictures of the apple maggot to be sure you are notcounting a non-target species; pay particular attentionto the dark patterns in the wings, which differ in theapple maggot fly and the cherry fruit flies. First trapcaptures usually occur in early to mid-June. Growersshould spray when five apple maggot flies are trappedper ball (note: or one fly per trap if fruit volatile lure is

plumcurculio

adult

plumcurculio

larva

applemaggot

34

Apples and Pears

fruit-treeleafrollerlarva

not used). Season trapping needs include three red balltraps and three hangers, three fruit volatile lures (note:not a pheromone), and one tube or can of Tanglefoot.The fruit volatile lure lasts all season and does not needto be replaced periodically.

Chemical Control: Control of the apple maggotneeds to be directed at the adult flies before egglaying occurs. Additional sprays may be needed iftraps’ catch counts remain above five flies. Often incommercial orchards, sprays applied to the firstseveral border rows are sufficient to control applemaggot flies entering the orchard.

Pear Psylla(Cacopsylla pyricola; order Homoptera, family Psyllidae)

Damage: The most troublesome insect pest of pearsis usually the pear psylla. It sucks plant sap andinjects a toxin into leaves as it feeds, causing wiltingand leaf drop. It may take the tree several years torecover from the reduction in vigor. Psyllaexcretes honeydew on leaves, which can kill leaftissue and lead to a condition known as psyllascorch. Black sooty mold can grow on honeydew,which can further affect the appearance and vigor ofpears.

Appearance: The pear psylla is a small insect, only1/10-inch when fully grown. The adult has a stoutbody with a wide head and thorax, red eyes, andwings longer than the body. The clear wings are heldroof-like over the sides of the body. It looks like aminiature cicada. Eggs are yellowish orange and maybe seen with the aid of a magnifier. Newly hatchednymphs are yellowish, 1/80-inch. Late-stage nymphsare hard shelled, and wing pads are apparent.

Life Cycle and Habits: Adults overwinter on the treesin bark crevices. Adults emerge, mate, and beginlaying eggs when temperatures reach 50° to60°F. Eggs are deposited increvices in the bark and near theterminal buds. Most eggs hatchby petal fall. Nymphs move tothe axils of leaf petioles andyoung fruit to feed. Five nymphalstages are passed before the adults

appear. Females of the later generations deposit mostof the eggs along the leaf midribs. There are three tofour generations per year.

Monitoring and Thresholds: Look for adults onspurs and branches on warm days just before budburst, and on the tender new shoots the remainder ofthe season. Eggs in late dormant to bud burst arefound singly or in rows on spurs and twigs or aroundbud scales. Through the remainder of the season,look on the undersides of tender new growth for rowsof eggs along the leaf midribs. Small nymphs arefound from green cluster throughout the season ontender new growth; larger nymphs are found onleaves that are hardening off. Nymphs and adults canbe monitored with beat cloths and adults with yellowsticky cards.

Chemical Control: Pear psylla is difficult tocontrol and has become resistant to

many insecticides. A delayed dormantoil should be applied as adults are

emerging, but before egg laying hasoccurred. This is green tip in most years, but

monitoring will determine more exact timing. Themost important times to treat for pear psylla are atthe pre-bloom (white bud) and petal fall stages.

Leafrollers(order Lepidoptera, family Tortricidae)RED-BANDED LEAFROLLER (Argyrotaenia velutinana)OBLIQUE-BANDED LEAFROLLER (Choristoneura rosaceana)FRUIT-TREE LEAFROLLER (Archips argyrospila)

Damage: Red-banded leafroller larvae feed on applefoliage and fruit, with the last generation of theseason doing the most serious damage. The larvaattaches a leaf to the fruit surface with silk and feedson apple skin and flesh. Some other species ofleafrollers that can be found in the Midwest includethe oblique-banded leafroller and fruit-tree leafroller.

Appearance: The red-banded leafroller is brown,about the size of the codling moth, and has broadreddish bands on each forewing. Larvae are green andslender with a light brown head; they reach a lengthof about 2/3-inch. The oblique-banded leafroller isbrown with three dark bands on the front wings.Wing spread is about 1 inch. Larvae are small and

pear psyllaadult

pear psyllanymph

35

Apples and Pears

green with black heads. Thefruit-tree leafroller is a

brown moth slightly largerthan the codling moth.Thin light markings appear

in various patterns across the front wings. The larva isa slender, pale green worm. The head is black with ablack spot just behind the head. The larva reachabout 3/4-inch in length.

Life Cycle and Habits: The red-banded leafrolleroverwinters as a pupa in debris on the ground. Adultsemerge in early spring and lay eggs in masses onundersides of larger limbs. Eggs hatch at aboutbloom. Newly hatched larvae fold or roll leavestogether with webbing and feed onfoliage. There are second, third, andfourth generations in southern areasof the Midwest.

The fruit-tree leafroller overwintersin the egg stage on twigs. Hatchoccurs about the time buds begin toopen. Larvae feed on buds, blooms,leaves, and fruits. In June, fullygrown larvae pupate inside folded orrolled-up leaves. Moths appear 2weeks later, lay their eggs, and die.Only one generation occurs each year.

Overwintering of the oblique-banded leafrolleroccurs as partially grown larvae inside tightly wovencases on the host trees. During spring, larvae emergeand feed until late May. Pupation occurs, and adultsemerge in June. One or two generations may occureach year. Damage is done by young larvae miningthe leaves, with larger larvae feeding inside rolled-upleaves.

Monitoring and Thresholds: Leafroller populationscan be sampled by both tree examination andpheromone traps. Because these species have widehost ranges, pheromone trap catch numbers are oflimited value in determining economic thresholdsand the need to spray. Pheromone trap catches willindicate when to monitor carefully for the larvae.Pheromone traps should be in place by the green tipfor red-banded leafroller, pink for fruit-tree leafroller,

and mid-May for oblique-banded leafrollerand maintained through September. Monitorfor larvae by examining the number of larvaeper 100 expanding leaf terminals or fruit clusters. Usean average of four larvae per 100 expanding leafterminals or fruit clusters for making managementdecisions.

Chemical Control: In the Midwest, cover sprays forcodling moths and other orchard pests usuallycontrol leafrollers as well. Egg hatch of the red-banded leafroller often coincides with petal fall, sosprays applied at this time will control it. In someareas, the oblique-banded leafroller has becomeresistant to organophosphate insecticides, so chemi-cals with different modes of action may be required.

Tufted Apple Budmoth(Platynota idaeusalis; order Lepidoptera, family Tortricidae)

Damage: Young larvae of tufted apple budmoth feedalong midribs of leaves, then bite into the petiole tomake a characteristic notch. Like other leafrollers,older larvae of the tufted apple budmoth use webbingto attach a leaf to a fruit, then they chew on the surfaceof the fruit underneath the leaf. Fruit damage is similarto that of red-banded leafroller, but the budmoth-damaged patches are usually smaller and moreseparated than the more continuous patches of feedingdamage caused by red-banded leafroller. Characteristicfruit damage by tufted apple budmoth is the same asthat of the variegated leafroller (Platynota flavedana),which is the major leafroller in central Virginia andparts of West Virginia. Tufted apple budmoth is themajor leafroller in Pennsylvania and other mid-Atlanticstates. It is present in the Midwest but is not as seriousa pest as it is in Pennsylvania.

Appearance: Fully grown larvae are 3/4-inch long,light grayish brown with a dark stripe down the back,and they have a chestnut brown head capsule and adark brown plate just behind the head. Egg massesare flat, dime-sized, and contain about 150 eggs; eggsare green when freshly laid and bronze when close tohatching. Adults are small moths that are mottledgrayish brown, lighter at the wing base, and darker atwing tips. There are tufts of scales on the top of themiddle of the forewings.

red-bandedleafroller

fruit treeleafroller

adult

oblique-bandedleafroller

36

Apples and Pears

Life Cycle and Habits: Tufted apple budmothoverwinters as larvae in rolled leaves beneath fruittrees. Adults emerge in early May and lay eggs on theupper surface of leaves. Eggs hatch in 10 to 14 days.First generation eggs hatch in June. Second genera-tion eggs hatch in August. There are two generationsper year.

Cultural Control: Remove apple suckers and suppressthe groundcover under apple trees to eliminate theearly spring habitat of tufted apple budmoth.

Monitoring and Thresholds: A sex pheromone trapis available to monitor adult males of this species. Useone trap per block if less than 5 acres, or two trapsper block if more than 5 acres. Set up traps by thefirst of May. Attach the trap to a limb in the outerthird of the tree canopy, at a 5- to 6-foot height. Fruitdamage is usually negligible if there are fewer than 50moths per trap during the 3-week period after thefirst moth is caught. If the number of moths per trapduring the 3-week period after the first moth iscaught is 100, then about 3 percent of fruit is likelyto be damaged at harvest; if 200 moths are trapped,then about 9 percent fruit damage is predicted atharvest.

Chemical Control: Insecticide is effective if usedwhen eggs are hatching and larvae are small, beforethey are protected within rolled leaves. The best timeto spray to control the first brood is when 10 percentof eggs have hatched, which is 530 degree-days (base45°F) after the first moth was caught in a pheromonetrap, and spray again after 60 percent of eggs havehatched, which is 805 degree-days after the first mothwas trapped. The best time to spray to control thesecond brood is at 10 percent egg hatch, which is2,280 degree-days (base 45°F) after the first mothwas caught, and spray again after 60 percent egghatch, which is 2,665 degree-days after the first mothwas trapped. Control is improved if spray volume isat least 100 gallons per acre.

San Jose Scale(Quadraspidiotus pericosus; order Homoptera, familyDiaspididae)

Damage: San Jose scale can infest apples, pears,peaches, and plums. The young crawlers feed onlimbs, leaves, and fruit, causing red, spotted areas.Infested leaves usually drop, and limbs lose vigor anddie. Fruit will have an undesirable finish because ofthe red, spotted appearance caused by scale feedingand the presence of the scale.

Appearance: The yellow female is underneath a gray,round, and flattened scale-like cap. When mature, thescale is about 1/20-inch in size. The male is a tiny,yellow, two-winged, gnat-like insect. Theminute crawlers are orange-yellow and oval,and they have six legs.

Life Cycle and Habits: San Jose scaleoverwinters as a nymph under a scale on treelimbs and resumes feeding when sap begins to flow inthe tree. In the spring, adult males emerge aboutmid-May and seek out wingless females. Matingoccurs and crawlers emerge about 1 month later.These tiny yellow insects move around on bark,foliage, and fruit until they locate a suitable site tosettle down permanently. Once settled, the crawlersticks its mouthparts into the tree and secretes a waxyshell over its body. There are two or more generationsper year.

Monitoring and Thresholds: Scale should bemonitored by two methods: 1) adult traps about 2months in early spring and 2) the appearance of thecrawler stage. Assemble traps and hang in scale-infested trees by April 1. At least twice per week,remove each trap from the tree and examine thesurface with a hand lens (magnifier) for adult scales.Once adult scales have been captured, begin calculat-ing degree-day accumulation (see “Chemical Con-trol”). Crawlers can be detected easily by wrapping asmall amount of black electrical tape with the stickyside out around an infested limb. Pay particularattention to the edge of the tape. Crawlers also can bedetected with a hand lens and a straight pin to probeor “flip” over mature scales and look for tiny, orange-yellow crawlers.

San Jose scale

37

Apples and Pears

The presence of reddish blemishes on fruit at harvestindicates damaging numbers on the trees. If suchdamage is noted, inspect bark of trees for scale,especially 1-year-old wood. During pruning opera-tions, look for purplish red halos on young bark thatare indications of scale infestation. Often this verysmall insect goes unnoticed until large populationshave developed. Growers should be on the lookoutfor scale on the fruit at harvest and evidence of scaleon new wood during pruning.

Chemical Control: Because this insect spends muchof its life cycle under a protective cover or scale,timing of insecticide applications is very important.Sprays should be applied when crawlers are observedor 400 degree-days (base 51°F) after adults are

captured. Insecticidal control is most effectivewhen used in conjunction with a well-applieddormant oil and a good pruning and training

program. Usually, dormant oil applications aremore effective against scale than delayed-

dormant applications.

Tarnished Plant Bug(Lygus lineolaris; order Heteroptera, family Miridae)

Damage: Their feeding with piercing, suckingmouthparts on fruit when it is very small causes deepdepressions or dimples in apples and pears that arenoticeable at harvest time. Several species of Lygus cancause similar damage to apples.

Appearance: Adults are 1/4-inch long, mottledbrown insects with wings folded over the abdomen. Ayellow-tipped triangle is present in the middle oftheir backs. Nymphs are small and greenish andresemble the adult without wings. Both nymphs andadults have a beak used for sucking plant juices. Theymove rapidly when disturbed.

Life Cycle and Habits: Adult tarnished plant bugsoverwinter under bark, in leaf litter, and in other suchprotected places. The adult feeds on opening buds orflowers in early spring, and later on developing fruit.They lay eggs in the plant tissue of their many hosts.Nymphs emerge about 1 week later and feed for about3 weeks before reaching adulthood. Several generations

of this insect occur each year. They are often abundanton pigweed and other flowering weeds.

Monitoring and Thresholds: Pay particular attentionto plant bugs before bloom. Adults aredifficult to find in trees and will flywhen disturbed. Hold a beat clothunder a scaffold, and strike the scaffoldsharply once or twice with the mallet.Sample five scaffold limbs per tree.Examine 100 fruit clusters for tarnished plant bugs;the threshold is five nymphs or adults per 100 fruitclusters.

Cultural Control: Tarnished plant bugs overwinterin, feed on, and may build up in number on ground-cover plants. Cover crop management is important toprevent tarnished plant bugs from moving into fruittrees. Because tarnished plant bug is attracted toflowering broadleaf weeds, management of annualweeds through regular mowing is an importantpractice for this pest.

Chemical Control: Control is most effective at thepink stage. This insect also damages young peachbuds, causing deformed fruit at harvest. Sprays at thepink stage to peaches are effective for its control.

Spotted Tentiform Leafminer(Phyllonorycter blancardella; order Lepidoptera, familyGracillariidae)

Damage: The larva of this moth is a leafminer thatfeeds inside the leaf between the upper and lowersurfaces. At first, the new mines are visible only onthe bottom surface of the leaves as a pale blotch. Asthe leafminer grows, the mine can be seen on the topof the leaf; it looks like a circle of speckles about1/2-inch in diameter. High populations can causesevere defoliation, leading to reduced fruit andterminal growth, early leaf drop, and reduced fruit setthe following season.

Appearance: Adults are 1/8-inch long, golden brownmoths with white spots or bands. The eggs are small,flat, elliptical, and laid singly on the undersides ofleaves. Eggs are transparent early, but soon turncreamy to yellow. Small larvae are extremely flat and

tarnished plantbug adult

tarnishedplant bugnymph

spottedtentiformleafmineryounglarva

38

Apples and Pears

legless; they live in the small space between leafsurfaces. Larger larvae have visible legs and a headcapsule and thus more closely resemble caterpillarsthan the small larvae.

Life Cycle and Habits: This insect overwinters aspupae in leaf litter. Small eggs are laid singly on theundersides of leaves. Small larvae begin to appeararound bloom. These larvae feed in a “U” shapepattern which delineates the area that will be themine. This is normally only visible from the under-side of the leaf. Larger, tissue-feeding larvae feed onboth the upper and lower leaf surfaces. After about amonth of feeding, larvae pupate within the mine, andadults begin to appear in about another month. Thisinsect has three generations per year.

Monitoring and Thresholds: Pheromonetraps can be used to monitor adult activity

from green tip through harvest. The firstcatch usually occurs at green tip with the first

generation peak at early pink and the secondgeneration peak in late June. Scout for eggs at

pink or for larvae at petal fall and in July.

Scout for eggs of spotted tentiform leafminer at pinkstage. Use a hand lens to see the small, round,translucent eggs. Examine three fruit clusters eachfrom at least three trees, and count the number ofeggs on the undersides of the second, third, andfourth leaves in each cluster (start counting leavesfrom the bottom of the bud). If an average of nine ormore eggs per fruit cluster is detected at pink, thenuse an insecticide for leafminer larvae at petal fall. Iffewer than nine eggs per fruit cluster are detected atpink, then an insecticide for leafminer larvae willprobably not be needed at petal fall, but scout forearly mines at petal fall to help make the finaldecision.

Scout at petal fall for early mines of the first genera-tion. Early mines are visible only on the underside ofthe leaf, not on the top. Examine three fruit clustersfrom each of at least three trees, and count the numberof early mines on the undersides of the second, third,and fourth leaves in each cluster. If four or more newmines per fruit cluster are detected, then use aninsecticide for leafminer larvae at petal fall.

Scout in early to midsummer for early mines of thesecond generation of spotted tentiform leafminer.The ideal time to scout can be determined by using apheromone trap and degree-day counts; scoutingshould be done 500 to 700 degree-days, base 43°F,(about 3 weeks) after the number of leafminer mothsbegins to sharply increase in pheromone traps. Toscout in midsummer, examine five mature terminalleaves per tree from at least five trees, and count thenumber of new mines on the undersides of theseleaves. If 2 1/2 or more new mines per leaf aredetected, apply an insecticide effective against sap-feeding leafminer larvae.

Chemical Control: If leafminers have been a persis-tent problem in previous years, apply an insecticidespray targeted at adults at peak emergence. Ifleafminer has not been a persistent problem, then donot spray for adults, but scout for eggs at pink andfor young larvae at petal fall and in July.

This insect has developed resistance to Guthion,Imidan, and other commonly used cover sprays.Grower experience has shown that Provado or Agri-Mek applied at petal fall provides satisfactory season-long control and does not harm beneficial mites andinsects. A pyrethroid (Asana, Ambush, Pounce) orcarbamate (Lannate) can be used, but these may leadto mite outbreaks later in the season due to theirtoxicity to predatory mites.

White Apple, Rose, and PotatoLeafhoppers(order Homoptera, family Cicadellidae)WHITE APPLE LEAFHOPPER (Typhlocyba pomaria)ROSE LEAFHOPPER (Edwardsiana rosae)POTATO LEAFHOPPER (Empoasca fabae)

Damage: Whitish spots or stippling on upper leafsurface are evidence of white apple leafhopper androse leafhopper feeding. Sticky honeydew secretionsfrom leafhopper feeding frequently cover lower fruitsand are called “tar spotting.” Damage is caused bynymphs and adults removing chlorophyll and sapfrom the lower leaf surface which can affect fruitdevelopment and bud formation. Adults can be anuisance if they are abundant at harvest as they canbe inhaled by pickers. The potential for rose leafhop-

spottedtentiformleafminer

larva

spottedtentiformleafminer

adult

39

Apples and Pears

per is largely dependent on the density and proximityto orchards of the primary overwintering host,floribunda rose.

Damage by potato leafhopper is less common and ischaracterized by yellowing and necrotic leaf margins.While these damaged areas are typically V-shaped,intense feeding can cause the entire leaf margin to beaffected. The bronzed, dried appearance of leaf tips isreferred to as “hopper burn.” Leaf margins on injuredleaves often curl downward. While white appleleafhopper is found on cluster leaves and not onactively growing terminal shoots, potato leafhopper ismore of a threat to young, nonbearing fruit trees andyoung, tender foliage.

Appearance: White apple leafhopper and roseleafhopper adults are very similar in appearance. Thelong, slender adults are wedge-shaped, with a convexback. The body is a light yellow, and the head isslightly darker. Juveniles are generally pale white andwingless; they scurry around when disturbed. While

white apple leafhopper nymphs are withoutnoticeable markings, older rose leafhoppernymphs have a few small black spots on theback of the thorax and wingpads.

Potato leafhopper is light green. White appleleafhopper can be distinguished from potato

leafhopper by the tendency of white apple leafhop-per to walk forward and backward, while potatoleafhopper walks sideways as well as forward andbackward.

Life Cycle and Habit: White apple leafhopperoverwintering eggs begin hatching at pink, andhatching is usually complete by petal fall. Thenymphs move to the undersides of the leaves to feed.First-generation adults begin to appear in June. Thereare two generations of white apple leafhopper peryear. The second generation adults are often notice-able during harvest.

Rose leafhopper overwinters as eggs on wild roses andbrambles. Nymphs emerge in the spring and feed onthe wild hosts. In June, adults disperse and move toapples. The second and third generations feed onapples.

Potato leafhopper develops throughout the year inthe southern United States near the Gulf of Mexicoand migrates northward each growing season ratherthan overwintering in northern states. The appear-ance of potato leafhopper is therefore less predictablebecause its migration depends on the jet stream andweather patterns.

Monitoring and Thresholds: Scout from bloomthrough petal fall for nymphs of the white appleleafhopper. Examine a leaf from the middle of a fruitcluster on 25 clusters on each of five trees. If anaverage of three or more nymphs per leaf is detected,then use an insecticide specifically targeted forleafhopper in addition to your cover spray insecticideat petal fall. With the rose leafhopper, and the secondgeneration of white apple leafhopper, examine 25leaves per tree and treat with an insecticide if there isan average of three or more nymphs per leaf.

Growers should monitor young apple plantings forpotato leafhopper and initial signs of damage.Consider treatment of young blocks when potatoleafhoppers first appear, particularly where they havebeen a problem in the past.

Chemical Control: The white apple leafhopperhas become resistant to commonly used cover

spray insecticides, such as Guthion andImidan. Provado is very effectiveagainst this insect, and it is lessdisruptive on mite management. In

orchards where leafhoppers have becometroublesome, it is important to include an effectiveleafhopper control in the first cover spray. Youngleafhoppers are easier to control than adults. Thefirst brood is an easier target than the second broodbecause the hatch is more synchronous.

European Red Mite(Panonychus ulmi; order Acari, family Tetranychidae)

Damage: European red mites feed by withdrawingjuices and chlorophyll from leaves and can build upto the point where leaf bronzing is visible by mid- tolate July. Under such conditions, mites can causeserious injury to the current year’s crop. Injury will beexpressed on fruit as poor color or a reduction in size

white appleleafhopper

adult

white appleleafhoppernymph

40

Apples and Pears

and quality. If damage is both heavy and earlyenough in early to midsummer, the next year’s cropcan be affected by a reduction in the number of fruitbuds. The earlier mites build up in the growingseason, the more serious the potential injury.

Appearance: This mite is red, with newly emergingfemales being bright velvety red, changing with timeto brick red. There are often noticeable white spots atthe base of six to eight hairs on its back. Males aredull green to yellowish brown. Females are moreglobular shaped; males are narrower with a morepointed abdomen. Eggs are of two forms. Overwin-tering eggs are red-orange and globular and some-what flattened (onion shaped) with a slender stalk ontop. Eggs produced during the growing season areyellowish orange and spherical without the stalk. Thefirst mite stage (instar) has six legs andsucceeding instars have eight legs.

Life Cycle and Habits: Overwintering occurs aseggs laid in roughened bark around the bases ofbuds and spurs. Egg hatch in the spring beginsaround tight cluster stage. Newly hatched mite larvaecrawl onto the unfolding leaves and begin feeding. Thelife stages are egg, larva, protonymph, duetonymph,and adult, with a resting stage between each activestage. Development from egg to adult may take from 1to 3 weeks and is very temperature dependent. Therecan be six to eight overlapping generations per season.Summer eggs are laid on the undersides of leaves,unlike winter eggs that are laid on twigs and branches.

Monitoring and Thresholds: Scout for European redmite each week from petal fall to August. Start bytaking four leaves from each of five trees, examinethem for the presence or absence of mites (do notcount the number of mites per leaf, just rate each asinfested or not infested). Then refer to the mitesampling charts (Figure 6) that correspond to theappropriate time: early season, mid-season, or late-season. On the chart, plot a point that shows howmany infested leaves you found in your 20-leafsample. The point will fall in one of three decisionzones: treat with a miticide, do not treat, or takeadditional samples. If the point on the chart falls in a“continue” zone, then collect leaves from additional

trees until you reach a decision. The maximumnumber of leaves to examine is 100 per block.

Biological Control: European red mite is rarely aserious pest in backyard and unmanaged orchards.Predatory mites, lady beetles, and the banded thripshelp to maintain European red mite at belowdamaging levels. This mite is considered a secondarypest; it typically builds to damaging levels only afterits natural enemies have been depleted by insecticideapplications used to control codling moth or otherpests. Minimizing insecticide usage and selectinginsecticides that are least toxic to beneficial organ-isms—in particular, avoiding the use of pyrethroidinsecticides—will help to minimize problems withthis mite.

Control with Oil: Over the years, a superioroil application applied close to the time miteshatch has proven to be one of the best controlpractices. The oil coats the eggshell, thereby

suffocating the developing mite embryoby blocking respiration. In recent years, a

number of orchards had mites thatshowed various degrees of resistanceto miticides. Because of this problem,

a good oil application becomes evenmore important during the dormant to delayeddormant period.

Chemical Control: Recent work has shown that tightcluster (Apollo), pink (Savey), or petal-fall miticide(Agri-Mek) sprays significantly help season-long mitecontrol, provided mite predators are conserved. Theuse of early miticides will often delay mite buildup,so that by late June or early July, very low populationsare present in the field. Because this coincides withthe establishment of mite predators, early controlmeasures often increase the likelihood of goodpredator-to-prey ratios, permitting the predator tokeep mites below treatment levels.

Growers routinely using early-season mite sprays ontheir mite-prone varieties should develop a plan tomanage the development of mite resistance to thesesprays. Apollo and Savey have very similar modes ofaction. Because of this, alternating Apollo and Saveyis a poor resistance management strategy.

Europeanred mite

female

Europeanred mitemale

41

Apples and Pears

During midsummer, Carzol, Pyramite, Kelthane, andsummer oils are rescue treatments that may be usedagainst established mite populations. Carzol,Kelthane, and Pyramite are highly toxic to mitepredators. In the summer, it may be necessary tomake two summer oil applications 7 to 10 days apartto reduce established populations. Carzol providescontrol of adults only and would have to be appliedrepeatedly to reduce mite populations. Kelthane givessome control of mites in cool and warm tempera-tures, but it should only be applied as a back-to-backapplication to the same generation of mites toprevent the buildup of resistance. Vendex provides along-residual control, but control is poor to fair.Pyramite is most effective against immature motilestages.

Aphids(order Homoptera, family Aphididae)ROSY APPLE APHID (Dysaphis plantaginea)GREEN APPLE APHID (Aphis pomi)APPLE GRAIN APHID (Rhopalosiphum fitchii)WOOLLY APPLE APHID (Eriosoma lanigerum)

Damage: Generally three species of aphids, the greenapple aphid, rosy apple aphid, and apple grain aphid,attack apple foliage in the Midwest. However, therosy apple aphid causes the most severe damage andis the most difficult of the three to control. Largenumbers of any type of aphid can stunt new growthand cause sooty mold to develop on fruit and leaves,but the rosy apple aphid injects a toxin with its salivathat causes the leaf to curl and the fruit to abort or tobe small or distorted. Relatively low numbers of rosyapple aphids can cause considerable damage. Prob-lems usually begin to appear at pink and into earlysummer before the aphids move to alternate hosts.Feeding by the woolly apple aphid on roots results inknots and stubby, gnarled root growth. Young treesare often severely injured by this pest. Althoughwoolly apple aphids feed above ground, the feedingon the roots produces the greatest damage.

Appearance: Apple aphids are small pear- to teardrop-shaped insects. Color varies from purple to gray to rosyfor rosy apple aphid, and to light green for green appleaphid and apple grain aphid. Generally a pair of pro-

90

80

70

60

50

40

30

20

10

020 30 40 50 60 70 80 90 100

Stop sampling and treat

Late-season Chartbased on a threshold of 7.5 mites per leaf

No treatment, resample in 11-16 days

Number of leaves examined

Tota

l lea

ves w

ith

mit

es

No treatment,resample in 6-10 days

90

80

70

60

50

40

30

20

10

020 30 40 50 60 70 80 90 100

Stop sampling and treat

Mid-season Chartbased on a threshold of 5 mites per leaf

No treatment, resample in 11-16 days

Number of leaves examined

Tota

l lea

ves w

ith

mit

es

No treatment,resample in 6-10 days

CONTINUE SAMPLING

CONTINUE SAMPLING

656055504540353025201510

5020 30 40 50 60 70 80 90 100

Stop sampling and treat

Early-season Chartbased on a threshold of 2.5 mites per leaf

No treatment, resample in 11-16 days

Number of leaves examined

Tota

l lea

ves w

ith

mit

es

No treatment,resample in 6-10 days

CONTINUE SAMPLING

CONTINUE SAMPLING

Procedure: Collect four leaves from each of five trees, examine them for presence or absence of mites, then plot the number on the chart. If the point falls in the continue zone, then collect leaves from additional trees until a decision is reached.

Source: Cornell Cooperative Extension Service, 1992 Pest Management Recommendations for Commercial Tree-Fruit Production.

CONTINUE SAMPLING

CONTINUE SAMPLING

Figure 6. European red mite sampling charts.

applegrainaphid

42

Apples and Pears

jections (cornicles) will be present on thefifth or sixth segment. Mouthparts are pierc-ing-sucking.

Woolly apple aphid colonies appear as acottony mass clustered in wounds of thetrunk and branches of the tree. The aphids them-selves are purplish, but are covered with waxy whitethreads.

Life Cycle and Habits: The life cycle of these aphidsbegins with the overwintering egg stage. Overwinter-ing eggs are found on twigs, around buds, or increvices in the bark. Eggs begin hatching in earlyspring about green-tip stage. The first generation ofnymphs are all wingless females, called stem mothers.These females give birth to live young, and a genera-tion is completed about every 14 days. In earlysummer, some winged young are produced; these flyto new host plants and start new colonies. Duringlate summer and early fall, both male and femaleforms are produced, which mate and lay overwinter-ing eggs. These eggs are green when first laid, butsoon turn shiny black as they mature.

The woolly apple aphid passes the winter in twoforms, the egg and the immature nymph. Nymphshibernate underground on roots of apple trees.Wherever apples and elms are close together, over-wintering eggs are deposited in cracks or protectedplaces on the elm. During spring, eggs hatch intowingless nymphs which feed on elm buds and leaves.In early June, a winged form is produced which

migrates to apples and other hosts. Theseindividuals feed on wounds in thebranches and trunk, and many worktheir way down to the roots and trunk

below ground surface. During thesummer, repeated generations of wingless

individuals will be produced. In the fall,winged individuals are produced which fly

back to the elm and lay overwintering eggs, whilesome wingless forms remain on the apple tree onboth aboveground and belowground parts through-out the winter. Now that elms are relatively uncom-mon, this aphid generally spends its entire life cycleonly on apples.

Cultural Control: Although all apple varietiesare attacked by rosy apple aphid, ‘Cortland,’‘Ida Red,’ and ‘Golden Delicious’ are particu-

larly susceptible. Rootstocks vary in susceptibilityto woolly apple aphid injury. Use MM.111 or

MM.106 if woolly apple aphid is a serious problem.

Monitoring and Thresholds: Apple growers shouldmonitor their trees carefully at pink for rosy appleaphids. A few colonies can rapidly infest the entiretree. Examine ten fruit clusters from the inner canopyof each of ten trees. If any rosy apple aphids arefound in this sample, then use an insecticide foraphid control at pink. If rosy aphid is not detected atpink, do not use an insecticide at pink unlessthe block has a history of economicinjury from plant bugs. After petalfall, treat for rosy apple aphid if 5percent of the terminals or fruitclusters have live colonies. A number ofpredators often control rosy apple aphid, so distortedleaves should be opened to determine if the aphids orpredators are still present before making controldecisions.

Monitor for green apple aphid from petal fall untilnew growth hardens off (usually by mid-July).Examine five terminals on each of five trees. Look foraphids and natural enemies, particularly the gallmidge larva (an orange maggot) that commonly preyson apple aphids. Treatment is suggested if 30 percentof the terminals are infested and natural enemies arenot present.

Careful examination of woolly apple aphid colonies isnecessary to determine if live aphids or predators arepresent. Predators can completely destroy an aphidcolony, but leave the waxy residue.

Chemical Control: Because rosy apple aphidinfestations will curl the leaves, early control isimportant. Once the leaves are tightly curled,adequate spray coverage and control are moredifficult. For that reason, rosy apple aphids are bestcontrolled at the pink stage of bud developmentwhile they are still exposed and before the serious leafcurl has occurred. The cover sprays for codling mothmay control light infestations of woolly apple aphid.

green appleaphid

rosy appleaphid

woolly appleaphid

43

Apples and Pears

Dogwood Borer(Synanthedon scitula; order Lepidoptera, family Sesiidae)

Damage: On young apple trees, dogwood borer cancause serious damage, possibly girdling trees. Thelarvae feed primarily in burrknot tissue on clonalrootstocks. All commercial dwarfing andsemi-dwarfing rootstocks have a tendency to developburrknots. As the burrknot tissue is consumed, thelarvae move outward and begin to feed on thecambium adjacent to the burrknot.

Appearance: The adult dogwood borer is a wasp-like,black and yellow, clearwing moth. With a wing spanof 3/4-inch, it is smaller than the peach borers. Thefemale has a wide yellow band on the fourth abdomi-nal segment; the male has a narrow yellow band onthe same segment. The larvae are white to pink, havea brown head capsule, and are 1/2-inch when fullygrown.

Life Cycle and Habits: The dogwood borer lays eggsin burrknot tissue or in graft unions on clonalrootstocks such as M.7, M.26, etc., or interstems; thelarvae tunnel throughout the burrknot tissue andadjacent cambial tissue. There is one generation peryear.

Monitoring and Thresholds: Pheromone traps canbe used from petal fall through harvest to monitor foradult dogwood borers. The first trap catch usuallyoccurs in late May or early June and peaks in earlyJuly. Control by trunk application at peak egg hatch,8 to 9 days after peak flight.

Cultural Control: White latex paint brushed on theexposed portion of the rootstock before egg layingbegins can prevent new infestations and also protectagainst southwest injury to the bark. Minimize theuse of plastic trunk guards, which create humidconditions on the trunk that are favorable to borerdevelopment.

Chemical Control: Infestations of dogwood borer areuncommon, and routine trunk sprays are notrecommended. But in orchards where dogwood boreris a problem, new infestations can be controlled byapplying an insecticide to the trunk at the time ofpeak egg hatch.

Cicadas(order Homoptera, family Cicadidae)PERIODICAL CICADA (Magicicada septendecim)ANNUAL CICADA (several species)

Damage: While periodicalcicadas emerge at 13- or17-year intervals, annualcicadas may be seen each year. The worst damageresults from egg laying when females slit the bark ontwigs and lay their eggs in the wounds. These smallbranches can turn brown and die, sometimesbreaking off. On young fruit trees, newly developedtrunk or scaffold branches can be so severely damagedthat new branches must be grown. Damage can besevere in newly planted orchards or new plantings ofshade trees or shrubs. Juvenile feeding on roots causesthe most long-term damage. Once nymphs haveburrowed into the ground and reached the roots, nocontrol method is available. During years onethrough five of an infestation, damage probably willnot be noticeable. However, for years 6 to 13 (or 17),juvenile cicadas may be extremely destructive toplants. Serious damage by annual cicadas is uncom-mon, and their activity in orchards is generallylimited to feeding.

Appearance: The periodical cicada and the annualcicada are confused because of superficial similarities.The periodical cicada is 1 1/2-inches long, with redeyes, a black body, and clearwings with orange veins;it appears from April to June. In contrast, the annualcicada is 2- to 2 1/2-inches long, with green eyes, agreen to black body, and light greenwings with dark green veins; itappears from July to September.

Life Cycle and Habits: After emergence and matingin late April through June, female periodical cicadaslay eggs in rows in pockets they cut in small branchesand twigs of trees with their knifelike egg layers.Females prefer grapevines and oak, hickory, apple,pear, and peach trees for egg laying. Eggs hatch in 6to 8 weeks. Nymphs fall to the ground and burrowdown to the root system where they stay for the next13 (or 17) years. Damage occurs as they use theirpiercing-sucking mouthparts to feed on the roots.

periodicalcicadanymph

periodicalcicadaadult

44

Apples and Pears

Cultural Control: Small trees can be covered with aprotective netting like cheesecloth secured at thebottom around the trunk. This covering will need tostay on for 4 to 6 weeks or until egg laying iscomplete. Since the trees are growing rapidly at thistime, care must be taken to keep the netting fromdeforming the scaffold branches. With older trees,damaged branches can be removed during winterpruning operations.

Chemical Control: Trees can also be sprayed.Orchards under a routine spray schedule may adjustthis schedule to coincide with the time when largenumbers of cicadas are present. Spray requirementswill vary depending on the severity of the outbreak.

Japanese Beetle(Popillia japonica; order Coleoptera, family Scarabaeidae)

Damage: The adult beetles feed on leaves of a widevariety of trees and shrubs. Adults feed on the uppersurface of foliage, chewing tissue between the veinsand leaving a lace-like skeleton of the leaf. Theyusually feed in groups, starting at the top of a plantand working downward. The beetles are most activeon warm, sunny days and prefer plants that are indirect sunlight. A single beetle does not eat much; itis group feeding by many beetles that results in severedamage. Trees that have been severely injured appearto have been scorched by fire. Japanese beetles willfeed on fruits that have been damaged by otherinsects.

Appearance: Adult Japanese beetles are3/8-inch-long, metallic green beetleswith copper-brown wing covers. A row

of white tufts of hair project fromunder the wing covers on each side

of the body.

Life Cycle and Habits: Japanese beetles overwinterunderground in the grub stage and pupate near thesoil surface in the spring. Grubs spend 10 months inthe soil where they feed on roots of grasses and can beserious pests of turf. Adults emerge from the groundand begin feeding on various plants in June. Activityis most intense over a 4- to 6-week period beginningin late June. By mid-July, numbers of beetles gradu-ally diminish. Individual beetles live about 30 to 45days. There is a single generation per year. Orchardtrees that may be severely attacked include apple,cherry, black cherry, peach, and plum.

Monitoring and Thresholds: There are few thresholdguidelines relative to when apples need to be treatedfor Japanese beetles. However, the first Japanesebeetle colonizers in the early summer will attractothers into the orchard, so early control can reducelater infestations.

Japanese beetle traps are available that lure both maleand female beetles into the trap. This trap is soeffective at attracting beetles that it can actuallyincrease both the number of beetles in the vicinity ofthe trap and the damage they cause. Despite the badreputation the trap has earned because of its super-attractiveness, the trap is still effectively used if it isplaced at some distance away from the orchard.

Chemical Control: Carbaryl is the most effectiveinsecticide used in managing Japanese beetles.However, because carbaryl can greatly increaseproblems with European red mites, other insecticidesare recommended to manage low to moderateJapanese beetle populations in apples. Repeatedinsecticide applications may be necessary at 7- to 10-day intervals to prevent reinfestation during the adultflight period or after heavy rains. Use of a spreader/sticker in the spray mix can increase the duration ofeffectiveness.

Japanesebeetle

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Apples and Pears

Summary of Insect and Mite Pest ManagementProcedures on Apples and Pears

Cultural controls when establishing a new orchard:• Choose a planting site with suitable soil and good

water drainage.• Remove alternate hosts for codling moth and

plum curculio.• Remove alternate hosts, especially brambles for

flyspeck and sooty blotch, and cedars for rust.• Purchase certified virus-free stock from a reputable

nursery.• Avoid rootstocks that are highly susceptible to

woolly apple aphid.• Avoid cultivars that are highly susceptible to rosy

apple aphid.• Avoid fire blight-susceptible rootstock/cultivar

combinations.

Cultural controls while maintaining an orchard:• Prune trees to ensure adequate spray coverage in

all parts of the trees.• Provide adequate but not excessive nitrogen

fertilizer, especially to fire blight-susceptible treesand to avoid flushes of growth attractive to aphids.

• Destroy fruit that falls in early to midsummer.• Prune to ensure good air circulation and adequate

spray coverage in all parts of the trees and toremove fire blight infections.

• Keep broadleaf groundcover under trees toenhance predatory mites.

• Keep orchard mowed to discourage tarnishedplant bug.

Monitoring for pests:Insect traps• Hang pheromone traps for leafrollers and spotted

tentiform leafminers in trees at green tip andexamine twice per week.

• Hang pheromone traps for San Jose scale at pinkand examine twice per week through May, or usesticky tape to monitor for crawlers from mid-Maythrough early June.

• Hang pheromone traps for codling moth at pinkand examine twice a week through harvest.

• In the northern Midwest, hang canary-yellowsticky traps and red spheres in early June to

monitor for apple maggot and maintain themthrough mid-August.

• Use degree-day forecasting to time spray applica-tions for San Jose scale and codling moth, inconjunction with pheromone traps.

Disease prediction• Use a commercial scab predictor or temperature

and leaf wetness measurements to monitor scabinfection periods.

• Use the MARYBLYT computer program tomonitor development of fire blight and predict theonset of symptoms.

Scouting• Pruning: look for scale injury to new wood.• Tight cluster through pink: look for plant bugs

and rosy apple aphid.• Tight cluster through first cover: look for aphids.• Petal fall through second cover: look for plum

curculio damage and leafhoppers.• Early June: begin looking for European red mite

and Japanese beetle.• Harvest: evaluate for San Jose scale, codling moth,

plum curculio, and leafroller control. Also,examine leaves, especially the undersides, for late-season scab.

Applying insecticides and miticides:• To minimize the emergence of pests that are

resistant to pesticides, avoid repeated applicationor season-long use of pesticides with the samemode of action.

• Use a delayed dormant oil application to controlEuropean red mite and San Jose scale.

• Use broad-spectrum insecticide only againstcodling moth, plum curculio, and leafrollers.

• Use narrow-spectrum insecticides if problems aredetected with aphids, leafhoppers, leafminers, andSan Jose scale.

• Avoid using products known to be highly toxic topredatory mites or predaceous insects.

Consider using mating disruption for codling mothmanagement.

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Apples and Pears

Apple Orchard Management Calendar

Pre

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Sum

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July

Aug

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Sept

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Har

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Dec

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Dormant Pruning, Brush Removal, Leaf ChoppingRidomil for Collar RotFertilizationPre-emergence HerbicidesSan Jose ScaleEuropean Red MitesSpotted Tentiform Leafminer Scab InfectionRosy Apple AphidGreen Apple AphidPowdery MildewRust InfectionsTarnished Plant BugFoliar Boron and NitrogenFire Blight InfectionsCodling MothPlum CurculioRed-banded Leafroller Chemical ThinningWhite Apple LeafhopperFruit RotsBlister SpotCork Spot and Bitter Pit Flyspeck and Sooty Blotch Apple MaggotOblique Banded LeafrollersJapanese BeetlePost-emergence HerbicidesIrrigationWatersprout and Sucker RemovalFoliar AnalysisPut out Rodent Bait.Trunk Borers

Put pheromone traps in place or begin taking environmental data for pest prediction.