A pple trees are popular in yardsand gardens throughout

Wisconsin. However, the moist, tem-perate climate of Wisconsin favors anumber of disease and insect peststhat must be managed in order toproduce high-quality fruit. Managingpests will also make trees more tol-erant of drought and cold and therebyprolong tree life.

This bulletin outlines basic princi-ples of pest management. While thisis not a guide to organic fruit produc-tion, where possible we haveincluded strategies that do not rely onpesticides (chemicals that kill pests).Pesticides are often used by commer-

cial apple growers because many ofthe non-chemical pest managementmethods are impractical for a largeorchard. Home gardens, however,usually contain only a few trees, andnon-chemical methods should formthe backbone of pest management.Limiting pesticide use in the homegarden is desirable for the health ofpeople, animals, and the beneficialmicrobes and insects, which far out-number the pests. Successful pestmanagement using few or no pesti-cide sprays depends on under-standing the pests’ life cycles andweather conditions that favor theirsurvival and growth. Further infor-mation on growing apples can befound in the publications listed onpage 12.

General pestmanagement strategies

Most people think about pestmanagement when they find wormyor scabby apples at harvest.Unfortunately, this is too late tomanage the pests that have alreadydamaged the fruit. Pest managementis a season-long endeavor that shouldbegin even before apple trees areplanted. Choosing a suitable plantingsite, fertilizing as needed, andtraining and pruning will help treesresist, or at least tolerate, theonslaught of pests. Some generalapproaches to pest management aredescribed below. Most commercialapple growers enjoy their greatestsuccess when they use a combinationof these methods in an integrated pestmanagement (IPM) program. IPM isalso successful in the home gardenand yard.Disease-resistant varieties

The cheapest, safest, and simplestway to manage pest problems is toavoid them. The most serious diseasesof apple can be avoided by plantingdisease-resistant varieties purchasedfrom a reputable nursery. InWisconsin the need for fungicides(pesticides used to control diseasescaused by fungi) can be eliminatedcompletely in most years by plantingapple varieties resistant to apple scab.See Extension publication AppleCultivars for Wisconsin (A2105) forinformation on the relative resistanceof apple varieties to diseases.

While no apple cultivars specifi-cally resistant to insects have been

pple pest managementfor home gardeners

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P A T T Y M C M A N U S , D A N M A H R , a n d T E R Y L R O P E R

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A P P L E P E S T M A N A G E M E N T

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developed, some varieties are moretolerant than others to certain types ofpests. For example, apple maggottends to be more of a problem onearly-maturing summer varietiesrather than on varieties that maturelater in the year.Intervention

Intervention includes trappinginsects to prevent them from dam-aging fruit (trapping is described inthe insect section). Intervention alsoincludes removing or eliminatingalternate hosts and reservoirs forpests. For example, raspberry andblackberry canes can harbor the fungithat cause flyspeck and sooty blotchon apple fruit. Juniper is the alternatehost for rust diseases of apple. Wildplum is an important host for plumcurculio, which also attacks apples.Obviously, it is not always possible or

desirable to destroy other plants forthe sake of a few apple trees!Sanitation

Many disease and insect pestsreproduce or spend the winter ondropped fruit or dead leaves andbranches. Therefore, it is a good prac-tice to remove fallen fruit and leavesand dead or broken branches. Insectsthat infest fruit complete their lifecycle after the fruits have fallen to theground; such fruit should be pickedup and destroyed as soon as possibleto remove the insects before they com-plete their life cycle.Pesticides

Pesticides can be applied eitherpreventatively (i.e., before pests ordamage are expected) or curatively(i.e., after pests have just reached thelevel at which they start to causedamage). The preventative approach

is relatively easy because you don’thave to take the time to monitor andidentify pests. However, this methodcan be expensive and wastefulbecause sprays are applied at weeklyor bi-weekly intervals, regardless ofwhether or not pests are present. Thecurative approach is kinder to theenvironment, especially beneficialinsects and microbes, but it requiresmonitoring pest numbers and theweather, and understanding pests’ lifecycles. For optimal tree health andyour personal safety, always followinstructions on the product label.

DiseasesSeveral different species of fungi,

bacteria, water molds, and virusescause diseases of apple trees. Fungicause most of the diseases found onapple trees in home gardens. Animportant exception is fire blight,which is caused by a bacterium.Diseases caused by viruses areusually not a problem on apple treesin Wisconsin and can be avoided bypurchasing high-quality stock fromreputable nurseries.

The life cycles of fungi, watermolds, bacteria, and viruses are verydifferent, as are the approaches todisease management. Knowingwhich type of pathogen you’redealing with is necessary to adoptsuitable management strategies.Many apple diseases also occur oncrabapple, pear, and related orna-mental trees; these plants will be con-tinuing sources of inoculum if youdon’t manage their diseases as well.Some of the more common diseasesand their management are describedbriefly below. For more information,refer to bulletins and web sites listedat the end of this publication. Yourcounty Extension office can assist youin diagnosing diseases and other pests.

Is organic apple production for you?

It’s difficult to get a high yield of undamaged apples using truly

organic methods. Even commercial organic orchards may experi-

ence losses of 25% or more, and they rely on relatively labor-

intensive methods. In some cases, frequent applications of

approved organic fungicides and insecticides are needed. If you

are willing to use conventional insecticides, you can usually

harvest a reasonably good crop with relatively few insecticide

applications. In fact, in Wisconsin, it’s likely that you can produce

better-quality fruit with fewer applications using synthetic pesti-

cides rather than approved organic pesticides. This is especially

true if growing varieties that are susceptible to apple scab.

3

� Apple scabApple scab is by far the most

common disease of apple andcrabapple trees in home gardens andyards. Fruit with scab have unsightlybrown to black lesions and, in severecases, deep cracks. Pear trees also getscab, but the pear scab pathogen doesnot infect apple. Planting scab-resistant varieties is the best way forthe home gardener to manage scab.Otherwise it is nearly impossible toproduce blemish-free apples withoutapplying fungicides.

The scab fungus overwinters infallen leaves. In the spring, fungalspores are ejected from leaves on theground. Thus, raking leaves in thefall and again in the spring as soon asthe snow melts will help reduce thedisease. Apple leaves are susceptibleto infection as soon as buds showgreen tissue in early spring. Infectioncan occur at temperatures as low as40°F if trees remain wet for severalhours. Thousands of new spores areproduced within a single scab lesion,and each spore is capable of starting anew infection. Therefore, if early-season infections are not prevented,scab will be a problem all season long,resulting in early defoliation andunattractive fruit. A tree with severescab will be prone to cold injury inthe subsequent winter and might notproduce fruit the following year.

Management. If you have vari-eties that are susceptible to scab, thefirst fungicide spray should be appliedwhen buds show 1⁄4 to 1⁄ 2 inch ofgreen tissue, especially if the weatheris rainy or foggy, or rain is predicted.(If the spray has had time to dry fol-lowing application, a moderate rainwill not wash it off.) Most fruit treefungicides found in garden centersare “protectants,” meaning theyshould be applied before infection.

Fungicides should be appliedevery 7 to 14 days through petal fall,unless the weather is exceptionallydry. If there are no scab lesionsshowing on leaves and young fruit by4 weeks after petal fall, then no moresprays will be needed to control thisdisease. However, if scab has devel-oped, additional sprays will be neces-sary to prevent fruit infections. Mostfruit tree fungicides are formulatedspecifically with scab in mind.� Fire blight

Fire blight can be deadly to appletrees and related plants. In highlysusceptible varieties, the disease isalmost impossible to control after ithas become established and theweather is warm and wet.

Fire blight is caused by a bac-terium that infects plants throughflowers and soft, succulent shootsand then spreads internallythroughout the tree.

Management. Apple varietiesand rootstocks differ greatly in theirlevel of resistance to fire blight. If therootstock becomes infected, the tree islikely to die. Therefore, you shouldespecially avoid susceptible varietiesgrafted to susceptible rootstocks.Excessive nitrogen fertilization alsoshould be avoided, as this promoteslush new growth, which is highlysusceptible to fire blight.

If fire blight infections are few,they can be pruned out during thegrowing season by cutting at least 10inches (more is better) below visiblesymptoms. If there are too manyinfections to remove, it’s best to post-pone pruning until winter when thebacterium is not active.

Chemicals have been inconsistentin controlling fire blight. Coppercompounds (e.g., Bordeaux mixture)may help kill bacteria that ooze fromcankers in the spring. The antibiotic

streptomycin protects flowers frominfection but does not control fireblight after symptoms have developed.

For more information about thisdisease, see Extension publicationApple, Pear, and Related Trees Disorder:Fire Blight (A1616).� Flyspeck and sooty blotch

Flyspeck and sooty blotch appearin late summer as clusters of blackdots (flyspeck) and black, sootysmudges (sooty blotch) on fruit. Thediseases affect yellow and red applevarieties similarly, but are much morenoticeable on lighter-colored apples.The fungi remain in the peel and donot affect the taste or texture of thefruit. The fungi that cause flyspeckand sooty blotch overwinter on manywoody plants, especially raspberryand blackberry canes. Dead or weak-ened apple wood (e.g., fire blightcankers) can also serve as a reservoirfor the fungi. Spores are spread bywind and rain during the summer.Disease development is favored byextended rainy periods, especiallywhen evening temperatures arewarm (65° to 70°F) and humid.

Management. To the extent pos-sible, remove any undesirable woodyplants, since these are potential reser-voirs for the fungi. Prune trees topromote air circulation and drying offruit and foliage.� Powdery mildew

Powdery mildew is a commondisease that can occur on almost allyard and garden plants. Unlike scab,however, powdery mildew is not amajor problem on apple every year inWisconsin. The fungus that causespowdery mildew on apple is differentfrom the species that infect otherplants such as lilacs and roses.

Management. Although thepowdery mildew fungal spores donot require rain to germinate and

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infect, infection is favored by humidconditions following rain. Therefore,to promote air circulation and reducerelative humidity within the treecanopy, prune trees in late winter. Manyof the scab-resistant varieties are alsofairly tolerant of powdery mildew.The fungus overwinters in apple budsand survives best during mild wintersand on apple trees growing nearheated buildings. The powderymildew fungus becomes active whenshoot growth starts in the spring, andthis is when chemical control is mosteffective.� Phytophthora rootand crown rot

Phytophthora root and crown rotsare caused by various species of thewater mold Phytophthora. Severalspecies of Phytophthora are common inWisconsin soils, but they only causeproblems for apple trees if the soiland/or base of the tree remain wet forseveral days at a time. Such condi-tions are more common in fall orspring, and this is when Phytophthorais most active. Phytophthora can causeroot rot or cankers on the trunk at orjust below the soil line (known as the

“crown”). Leaveson affected treesare generally

small and pale during early summerand turn reddish in late summer.Because apple trees can regenerateroots, a tree can recover from rootinfection if soils are moist but not sat-urated. Trees with crown rot maysurvive for a few years, but they gen-erally do not recover.

Management. Prevention is thebest way to manage this disease. It iscritical to choose a well-drained sitewhere water does not pool afterheavy rains. Planting in light, sandysoil is ideal. If soil is heavy, choose rel-atively resistant rootstocks such asM.9, Mark, Bud.118, Bud.9, and theGeneva (“G”) series; avoid highly sus-ceptible rootstocks such as MM.106and M.26. Heavy mulching keeps soilwet and should be avoided ifdrainage is less than ideal. Plastictrunk guards should be loosened orremoved during prolonged wetperiods. The area surrounding thetrunk should be kept free of tall grassand weeds that will retain moisture.

Managing Phytophthora diseasesof apple with chemicals is usuallyineffective, and the products availablefor this purpose generally are notcarried by garden centers.� Rust diseases (cedar applerust, quince rust, hawthorn rust)

Rust diseases of apple are causedby several related species of fungi.The rust fungi depend on variousspecies of juniper (especially Juniperusvirginiana, the eastern red cedar) tocomplete their life cycles. In thespring, fungal spores are carried up toa few miles from junipers to appletrees. Obviously, eliminating alljuniper trees in the vicinity of yourapple trees is not practical.

Management. Several applevarieties are highly resistant to cedarapple rust and should be used ifeastern red cedars are abundant in the

area. Unlike apple scab, rust lesionson apple do not produce spores thatcan reinfect apple; only spores fromjunipers will infect apple leaves andfruit. If fungicide sprays are used,they should be applied every 10 to 14days, especially if rain is anticipated,starting when apple flower bud clus-ters are separated (open cluster stage)through about a month after petal fall.

Insects and mitesOver 50 types of insects and mites

are known to damage apple trees andfruit, but a much smaller number rou-tinely cause sufficient damage to be ofconcern to home orchardists. Differenttypes of pests can attack the rootsystem, the trunk and branches, theleaves, and the fruit. Those pests thatdirectly attack the fruit are of biggestconcern in home apple production.There are four or five very commonpests that directly attack apple fruit,sometimes making the fruit totallyunusable. It is difficult to control someof these pests without at least someinsecticide use. Apple insects are socommon that it is impossible to growfruit without some losses unlesscontrol methods are used.

How much control is needed?For many people, a few bushels ofquality fruit are sufficient, especiallyif they don’t have a way to store them.If these are your expectations, youwill be able to grow apples withminimal insect control. On the otherhand, if you wish to produce a largecrop of high-quality fruit, your insectcontrol program will need to be morerigorous. People also have differingviews on the use of pesticides. Whilemany are comfortable with themargin of safety required by federalagencies, which is reflected in thelabel directions, others are more cau-tious and would prefer to use fewer

pesticides. Some people are comfort-able with “organic” pesticideswhereas others would prefer to use nopesticides at all.

We’ve organized the control dis-cussion for each pest to reflect the dif-ferent options available, from a con-ventional insecticide-use program tooptions that are less dependent onsuch products. Keep in mind that forsome major pests, “least toxic”options may be fairly ineffective orcompletely unavailable. Also beaware that organic insecticides are notnontoxic; indeed, pyrethrum, anapproved organic insecticide, is actu-ally more hazardous to humans thanis malathion, a commonly used syn-thetic insecticide. Further, becausemany organic insecticides break downvery rapidly after they are sprayed,they often have to be used more fre-quently than synthetic insecticides toachieve the same level of control.

You should be able to get a highpercentage of good quality fruit withonly two to four insecticide applica-tions per year, especially if you arewilling to use conventional insecti-cides that generally provide up to2 weeks of protection. The criticalspray periods are at petal fall and 2 to3 weeks after, and then from mid-Julyto mid-August. For more detailedspray timing, refer to the table.

Insect monitoring. One way toachieve good insect control withminimal use of pesticides is toexamine the trees regularly to evaluatelevels of pest activity. For example,very small developing fruit should beexamined every 3 to 4 days for about2 to 3 weeks after flowering to lookfor crescent-shaped slits caused byplum curculio. This damage is readilyseen. If an unacceptable number offruit are being damaged, controlshould begin immediately.

One method of monitoring whencertain insects are present is to useinsect traps. (A list of suppliers is pro-vided at the end of this publication.)For moths such as leafrollers, codlingmoth, and leafminers, use sticky trapsbaited with a synthetic version of theinsect’s mating pheromone. Thesetraps catch only males, not the egg-laying females, and therefore are noteffective for control. However, byknowing when the insects are flying,you’ll know when eggs are being laidand when insecticides should be used.If you keep track of the numbers ofinsects trapped from year to year,you’ll also know whether a particularpest is more abundant than normal.Apple maggot traps are red stickyspheres that mimic a ripe apple; theyare baited with an odor similar to ripefruit. Unlike sticky traps, this type oftrap can be used both to monitor andcontrol apple maggots.

The most serious fruit pests ofapple occur throughout the entiregrowing season, from the time thefruit start to develop until harvest.Plum curculio and leafroller damagecan begin a day or two after petal fall;codling moth starts about 5 to 10 dayslater, with a second generation insummer; and apple maggot damagecan be seen from early July intoSeptember. It’s important to knowwhich of these insects are causingproblems—only then will you be ableto develop a control program that ismost effective but with the least input.Your county Extension office will beable to help you diagnose insectinjury.Fruit-damaging insects

The most troublesome insects forhome apple growers are those thatdirectly attack the apple fruit.Following are brief summaries of thebiology, damage, and control of the

most commonly encountered applepests. More detailed information onthese and other insects is found in thebulletin Growing Apples in Wisconsin(A3565).� Apple maggot

The adult apple maggot is a flythat lays its eggs under the skin ofripening apples. The eggs hatch intotiny maggots (called railroad worms)that tunnel through the fruit, leavingdiscolored trails. As the fruit starts todecompose, it falls from the tree.Apples that are infested at harvestmay appear sound, but will rot instorage. There is one generation peryear, but the egg-laying period islengthy, from early July to late Augustor even early September. Early-maturing varieties tend to be morereadily attacked than late-maturingvarieties.

Management.Apple maggot isprobably the most serious insectproblem affecting Wisconsin homeapple production. The apple maggotfly is a strong flier that dispersesreadily to find new plantings to infest.If left uncontrolled, a substantial pro-portion of fruit will often be attacked.Hawthorn fruits are the natural hostof apple maggots and may serve as areservoir of apple maggots; wild anduntended apple trees also serve asreservoirs.

Low toxicity control program.Apple maggot is the only apple pestthat can be controlled fairly effectivelyby trapping. Female flies are attracted

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apple maggot

to baited, sticky red spheres. Hangtraps in trees about 5 feet above theground by the first of July. Maintaintraps through early September byreplenishing the lure (check packageinstructions for timing), and bycleaning the traps and reapplyingsticky material if they become coatedwith insects, leaves, or dirt. For bestcontrol, use one trap per 50 to 100fruit.

Intermediate to conventional

insecticide program. Approvedorganic insecticides are relatively inef-fective against this pest because theybreak down rapidly after sprayingand the adult flies are strong flierscapable of rapidly reinfesting treesfrom other areas. Conventional insec-ticides remain active for about 2 weeksafter spraying and therefore providelonger control with fewer applica-tions.

Apple maggot traps can be usedfor monitoring as well as control. Formonitoring, only a couple of traps areneeded for a small home orchard.Place traps in trees in late June andinspect twice weekly for apple maggotflies. For optimal control, apply aspray as soon as the first fly is caught.Conventional insecticides need to beapplied only at 2-week intervals,regardless of whether or not addi-tional flies are caught in the traps.Continue spraying every 2 weeks asnew flies are trapped. If you prefernot to use traps, spray during the firstweek in July and repeat at 2- to 3-weekintervals until the end of August.Generally, relatively good results canbe obtained with a series of threeapplications about 3 weeks apart, inearly July, late July, and mid-August.

■ Caterpillars—leafrollers and

green fruitworms

There are several types of cater-pillars (moth larvae), all of whichcause similar damage. Most injuryoccurs soon after fruit set, when thelarvae feed on the fruit surface,removing the skin and underlyingflesh. The damage usually heals,leaving a brown, corky, surface scar,but with the remainder of the affectedfruit sound and usable. These insectsalso feed on foliage, especially before,during, and shortly after the blossomperiod, but foliage feeding is usuallynot extensive enough to hurt the tree,or to reduce fruit quality or yield.

Management. Caterpillars arefrequently attacked by beneficialnatural enemies, including manytypes of predatory and parasiticinsects. Therefore, although thereusually are some caterpillars present,generally the numbers are fairly lowand damage is less than 5 to 10%. Insevere outbreaks, however, damagemay be much greater. Because theinjury is only on the fruit surface andthe wound usually is self-healing, thedamage is easily cut away when theharvested fruit are being prepared foruse. Therefore, many home applegrowers may choose to ignore thisdamage and not do anything tocontrol these insects.

Low toxicity control program. Donothing and accept that some fruitwill be damaged, but that theseapples can be used for sauce orbaking. However, keep an eye on theamount of damage from year to year;if populations build it may be neces-sary to treat.

Intermediate insecticide program.

Sprays containing the living bac-terium Bacillus thuringiensis (Bt) areeffective for controlling leafrollers andfruitworms, and are considered safeand acceptable for organic produc-tion. Several brands are available;check with your local garden center.Spray residues are very short-livedand applications must be appliedonce before bloom, once duringbloom (Bt does not harm pollinators),and once or twice immediately at theend of the blossom period.

Conventional insecticide program.

Conventional insecticides effectivelycontrol these insects; refer to the table.The most important control time isjust after bloom (at petal fall); delayswill result in some fruit scarring.Conventional insecticides must not beused during bloom to protect pollinators.Occasionally a second generation ofleafrollers hatches in midsummer;these can also be controlled with con-ventional insecticides.■ Codling moth

This is the proverbial “worm inthe apple.” The damage is easily rec-ognized by the rotted core with asingle straight tunnel to the outside,where the insect piles its waste mate-rial. The larva is often pinkish in colorand grows to about 2⁄ 3 inch long.There are usually two generations peryear, the first when fruit are youngand the second in mid- to latesummer. Infested fruit begin to rotinternally and often fall from the treebefore ripening.

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caterpillar

Management. This is a verycommon insect and one of the mostserious pests of apple. It is notunusual to see nearly the entire cropinfested in areas where the populationis high and no controls have beenapplied.

Low toxicity control program.There are no good options for lowinput control. This is a very commonpest but tends to be more of aproblem in some areas than in others.Codling moth females are relativelyweak fliers, and if your fruit trees areisolated from sources of infestationyou may be able to successfullyproduce sound fruit for many years.

However, it is likely that they willeventually become infested. Be sure topick up and destroy fallen fruit.

Intermediate insecticide program.Conventional insecticides are the bestoption for controlling codling moth;see the table. If the level of infestationin your area is moderate to low, andyou are willing to tolerate some fruitloss, two to four insecticide applica-tions per year (one for each genera-tion) may be sufficient. However,these need to be properly timed.Because the insects spend only a verybrief time on the outside of the fruit, aprotective layer of residual insecticidemust be present on the fruit when theeggs hatch. The first egg-layingperiod starts around the end of flow-ering and continues for 2 to 3 weeks.If you wish to make only a singleapplication, it should be timed forabout 5 to 10 days after the end ofbloom. You will get better control ofthe first generation with two applica-tions, the first made at about 7 daysafter petal fall and the second about2 weeks later. It is difficult to sayexactly when egg laying for thesecond generation will occur becauseof yearly differences in temperatures.For precise timing of sprays for bothgenerations, use pheromone moni-toring traps, as described in the insectmonitoring section.

Conventional insecticide program.For maximum fruit protection, sprayat petal fall and again at about 2-weekintervals for a total of three sprays forthe first generation. If necessary, maketwo to three additional applicationsfor second generation in mid- to latesummer.

� Plum curculioPlum curculio adults are a type of

weevil. Adult weevils overwinter inprotected locations, such as underfirewood, piles of brush, fallen leavesin woodlots, or in overgrownfencerows. They move into appletrees during the blossom period andfor 2 to 3 weeks after petal fall.

Female weevils take a few smallnibbles out of very young fruit andthen cut a small (3⁄16 inch) crescent-shaped slit into the surface of the fruitto lay eggs. As the damaged fruitsgrow, the affected areas becomelumpy and misshapen. Frequently theeggs do not successfully hatch inapples, so the grub-like larval stagemay not be present. There is only onegeneration per year, with damageoccurring usually within the first3 weeks after bloom.

Management. Plum curculio is anative insect that is best adapted forfeeding on stone fruits and tends to bemore of a problem in areas wherewild plum and wild cherry grow. Insome areas, plum curculio is veryabundant and, if not controlled, candamage a high percentage of the crop.When low to moderate populationsare present, the damage is primarilycosmetic and may be tolerable.Conventional insecticides readily

7

codling moth

plum curculioand damage

“Windfall” fruit that dropfrom the tree early are ofteninfested with insects, usuallyeither codling moth or applemaggot. These should be pickedup as soon as they fall and dis-carded, destroyed, or deeplyburied. If burying, cover appleswith at least 12 inches of soil.Leaving fruit on the ground orputting them whole onto acompost pile will allow insectsto complete their life cycle,resulting in further infestation.

control plum curculio; other methodsare less effective. If possible, removewild or abandoned host plants fromthe area to reduce overall populationlevels.

Low toxicity control program. Youcan jar plum curculio adults fromtrees by tapping limbs with a paddedstick or pipe. First place a sheet underthe portion of tree being tapped, andthen pick up the insects when theyfall to the sheet. This needs to be donetwo to three times per week for abouta month starting during the blossomperiod. This approach is more prac-tical and effective on small trees(young or dwarf) than on large trees.

Alternatively, many plum cur-culios approach a tree by walkingacross the ground rather than flying.Chickens readily eat these insects, anda fair level of control can be achievedby confining chickens to forage underthe trees from the blossom perioduntil about 3 weeks after petal fall. Donot allow chickens into areas thathave been treated with pesticides;read the pesticide labels regardingsuch precautions.

Rotenone is an approved organicinsecticide that is somewhat effectiveagainst plum curculio. It breaks downrapidly in the environment and needsto be applied at least weekly duringthe egg-laying period.

Intermediate to conventionalinsecticide program. Conventionalinsecticides readily control plum cur-culio. Generally two applications aresufficient, the first at petal fall and thesecond about 10 to 14 days later. Inareas of very high numbers, threeapplications may be necessary at10-day intervals. Refer to the table. Touse the least possible amount of insec-ticide, monitor young fruit twiceweekly starting a few days after petalfall, and do not treat until you seeegg-laying scars.

� AphidsVarious types of aphids feed on

apple foliage. Some produce a white,cottony, waxy material that is easilyseen. Others cause leaves to twist andcurl. Even though the damageappears dramatic, it usually is ofminor consequence to tree health orfruit quality. Aphids have manynatural enemies (predators, parasiticwasps, and fungal diseases) that keepthem in check. Large populations canbe controlled with insecticidal soapsor conventional insecticides.� Scale insects

A few types of scale insects attackapple trees. The most common is SanJose scale. These are very tiny insects,up to 1⁄16 of an inch in diameter andcovered with a grayish hard waxy“scale.” They usually feed onbranches, but may also feed on leavesand fruit. On green or yellow fruitthere is a red halo surrounding eachinsect. Scales are sap-sucking insectsand large numbers can severely stresstrees, even to the point of killingbranches. San Jose scale can be con-trolled before flowers open usingdormant oil sprays or by using con-ventional insecticides 1 to 3 weeksafter petal fall. Thorough coverage oftrunk and branches is essential.

� Spider mitesSpider mites are very tiny crea-

tures, only about 1⁄ 50 of an inch insize, and are usually dark reddish-brown in color. They feed on theleaves by sucking out sap and otherleaf components, including the greenchlorophyll. Usually spider mites areunder good biological control fromtiny predatory mites, as well ascommon predators such as ladybeetles and lacewings. In addition,heavy rains wash many off of trees,and high humidity slows theirfeeding and reproduction.Occasionally they occur in largeenough numbers to cause the leavesto turn bronze-colored; this affects theoverall health of the tree and mayreduce fruit size or quality. On smalltrees, many can be washed off with aforceful stream of water. Insecticidalsoaps and summer spray oils aresomewhat effective. If populations arehigh in late summer, thousands ofdeep red overwintering eggs may belaid around the tips of the stems;these are readily visible with a magni-fying glass. These can be controlledwith a dormant oil spray appliedbefore flowers open in the spring.

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Plant-damaging insects

aphid spider mite

San Josescale

spottedtentiform leafminer

Plant-damaging insects attack leaves, stems, orbranches. Usually there is no need to control for thesepests, but occasional intervention may be needed.

� Spotted tentiform leafminerSpotted tentiform leafminer is a

tiny caterpillar that feeds within theleaf, causing a speckled, blister-likeleaf mine about 3⁄4 inch long. Theseare common insects and a few minescan be found on almost every appletree. Low population levels do nothurt the trees or fruit. The insect isusually heavily parasitized by tinystingless wasps, and only occasionallyare enough present to cause damagein home orchards. The beneficialwasps are killed by conventionalinsecticides, and leafminer outbreaksmay be a sign of too much insecticideuse. By reducing unnecessary insecti-cide usage, the natural balance willeventually be regained.

Leafminers overwinter in fallenleaves. Raking and burning the leavesin the fall will kill a substantial portionof the overwintering population. Ifleaf mining becomes severe, insecti-cides containing permethrin or bifen-thrin are effective controls if properlytimed early in the insect’s life cycle.Once the mines are visible on theupper leaf surface, chemical control isnot effective. Petal fall is an importanttime to control. These products arebroad-spectrum insecticides whichwill be harmful to beneficial insects.

WeedsWeeds and other vegetation are

not typically thought of as pests, butthey may reduce yields and fruitquality by competing for light, water,and nutrients. They may also harborinsect and disease pests. Grasses areparticularly competitive. Many grasseshave expansive and finely dividedroots that intercept moisture andnutrients before they reach tree roots.Further, mowing or trimming close totrees can injure the trunks, especiallyon young trees. To limit weed compe-tition and to protect trunks from

insect, disease, and physical damage,keep a vegetation-free area that has a2- to 3-foot radius around each tree.Mechanical control

Mechanical control of vegetationincludes cultivation and mulches.Shallow cultivation every few weekswith a sharp hoe or shovel will elimi-nate young seedlings and olderweeds. Be careful not to damage thetrunk or roots growing near thesurface. Don’t use a rototiller neartrees, as this will harm them.Perennial weeds are the most difficultto manage using cultivation.

Amulch of wood chips, shreddedbark, sawdust, straw, or other organicmaterial can be used to inhibit weedgrowth. However, organic mulchesshould be kept to a minimum if thesoil is heavy or poorly drained.Decorative stones or gravel are alsoeffective, but will not offer completeweed control. Do not mound mulchesup against the trunk. Instead, spreadthem in a “donut” fashion, keepingthe deepest area several inches fromthe trunk. Mulches need to berenewed each year to remain effective.Killing existing vegetation with a non-residual herbicide before applyingmulches will give better results.

Some weed barrier fabrics arealso effective, but should be coveredwith an organic mulch to prevent sun-light damage to the fabric.Chemical control

Herbicides can be used to killweeds growing under apple trees.Check the label to ensure that they areregistered for use on specific plantsbefore applying. For controllingweeds that are already growing,apply glyphosate. Glyphosate killsactively growing annual and peren-nial weeds. It is a nonselective, non-residual herbicide that will kill desir-able plants as readily as weeds. It isselective only through selective appli-

cation. For the most benefit to appletrees, apply glyphosate in the springor early summer. Before spraying,thoroughly protect trunks of youngtrees with plastic wrap or aluminumfoil. Remove and discard the wraponce the spray has dried. Glyphosatemust be used according to label direc-tions. No residual herbicides are rec-ommended for home orchards.

Use of chemicalpesticides

While weeds are controlled byapplying herbicides to the ground,disease and insect pests are generallycontrolled by applying fungicides andinsecticides directly to trees. Thetiming of sprays, relative to treegrowth, is as important as the type ofspray used. The following table liststhe most appropriate chemicals andwhen to apply them. Garden centersvary in the products they carry.Therefore, rather than recommendingspecific products, we suggest youcheck product labels for active ingre-dients and then use the product asdirected on the label. Many general-purpose fruit tree sprays, sometimescalled “home orchard” sprays, containa fungicide such as captan plus one ormore insecticides (for example,malathion or carbaryl). While conve-nient, these sprays may result inexcessive insecticide use that can killbeneficial insects along with the pests.

The recommendations in the tableshould be similar to those on productlabels. However, if you find any dif-ferences, follow the directions on theproduct label. It is illegal and poten-tially dangerous to use pesticides in amanner inconsistent with the productlabel. Check labels and read the com-ments and footnotes in the table forimportant information about possibletoxicity to plants and incompatibilityof certain chemicals.

9

A P P L E P E S T M A N A G E M E N T

10

About this table

The insect control recommendations in the following table

relate to a more conventional insecticide program that will

maximize protection from insect injury. If you live in an area

with low insect pressure, or if you simply prefer to use fewer

pesticides, refer to the management recommendations for

each of the pests.

Spray schedule for apple trees

When to spray Pest Material Comments

Dormant—before any aphids, scale insects, dormant oil or � Thorough coverage of stems, branches, andgreen shows spider mites lime sulfur trunk is necessary for scale control.Green tip—when 1⁄4 to scab captan or � Leaf damage can result if captan is used within1⁄2 inch of green shows ferbam or 10 days of an oil application.

mancozeb or � Ferbam and mancozeb are known as EBDCmyclobutanil or fungicides. See product labels for limitationscoppera or when using EBDCs.sulfurb � Copper can damage leaves and fruit and should

not be used later than green tip.fire blight coppera � See footnotes on copper and sulfur.

Tight to open cluster— scab same as GREEN TIP � See footnote on sulfur.when flower buds are visible except no copper � An extra application may be needed if flower

buds take more than 10 days to develop frompowdery mildew sulfurb or open cluster to full bloom.

myclobutanil or � Ferbam and mancozeb are known as EBDCthiophanate-methyl fungicides. See product labels for limitations when

using EBDCs.rust ferbam or

mancozeb ormyclobutanil

Full bloom scab same as GREEN TIP � Streptomycin should only be applied ifexcept no copper temperatures are above 60°F and rain, heavy dew,

or fog prevail. Do not apply streptomycin after bloom.powdery mildew, same as TIGHT TO � Although some labels permit copper applicationrust OPEN CLUSTER during bloom to control fire blight, copper can injure

blossom and fruit tissue.fire blight streptomycinTo protect pollinating insects, do not use insecticides during bloom.

Spray timing

The date at which apple treesreach various developmental stagesdepends on the variety and weather.During a warm spring, trees movequickly from one stage to the next;during a cool spring, trees mayremain at a given stage for severaldays. For example, an extra scabspray may be needed between “opencluster” and “full bloom” if thisperiod lasts longer than 10 days,especially if there is rain. Sprays aregenerally not needed at intervalsshorter than 7 days.

11

Spray schedule for apple trees (continued)

When to spray Pest Material Comments

Petal fall—when more scab same as green tip � Carbaryl and permethrin have been associatedthan 75% of flower petals except no copper with outbreaks of spider mites when used frequentlyhave dropped on fruit trees.

powdery mildew, same as TIGHT TO � Permethrin cannot be used after petal fall.rust OPEN CLUSTER

aphids, bifenthrin orcaterpillars, carbarylc orcodling moth, esfenvalerate orplum curculio malathion or

permethrinFirst cover— scab captan or � To prevent residues on fruit and to stay within7 to 10 days after petal fall sulfurb product limitations, do not use mancozeb or

ferbam after petal fall.powdery mildew same as TIGHT TO

OPEN CLUSTER

rust myclobutanilcodling moth, bifenthrin orplum curculio, malathionSan Jose scale

Additional covers— scab captan or � If scab lesions are not visible 4 weeks afteras needed, at 10- to 14-day sulfurb petal fall, no additional scab sprays will be needed.intervals during the summer � Sulfur is only partially effective against flyspeck

flyspeck, captan or and sooty blotch. Sanitation and pruning duringsooty blotch sulfurb or winter are critical.

thiophanate-methyl � Sprays for apple maggot should start no earlierthan the first week of July.

aphids, carbarylc or � Carbaryl has been associated with outbreaks ofapple maggot, bifenthrin or spider mites when used frequently on fruit trees.codling moth, malathionleafrollers

a Copper is an active ingredient in many products. Bordeaux mixture (copper sulfate + hydrated lime) can damage fruit if applied later thangreen tip. Also, copper and lime are incompatible with certain other pesticides (e.g., captan), so check labels for these warnings.

b Sulfur should not be used on days when temperatures are expected to exceed 85°F as damage to foliage and fruit is possible.c Carbaryl can cause fruit to fall from the tree if applied within 3 to 4 weeks after bloom, until fruit is approximately 1 inch in diameter.

Additional informationFor related information on

growing apple trees, the followingpublications are available from yourcounty Extension office or from thepublications web site of University ofWisconsin-Extension CooperativeExtension: cecommerce.uwex.eduPublications

� General InformationApple Cultivars for Wisconsin (A2105)Fruit Crop Pollination (A3742-E)Growing Apples in Wisconsin (A3565)Home Fruit Cultivars for NorthernWisconsin (A2488)

Home Fruit Cultivars for SouthernWisconsin (A2582)

Rootstocks for Fruit Trees in Wisconsin(A3561)

Training and Pruning Apple Trees(A1959)

Walnut and Butternut Toxicity (A3182)When Are Apples Ripe? (A3743-E)� Disease and insect pestsApple Disorder: Sooty Blotch andFlyspeck (A3173)

Apple, Flowering Crab, Hawthorn,Juniper Disorder: Cedar-Rust Complex(A2598)

Apple, Pear, and Related Trees Disorder:Fire Blight (A1616)

Common Tree Fruit Pests (NCR063)Diseases of Tree Fruits in the East(NCR045)

Eastern Tent Caterpillar (A2933)Tree Fruits: Insect and DiseaseManagement for Backyard FruitGrowers In the Midwest (AIDEA3)

Watercore of Apple (A3280)Web sites

The following sites have usefulinformation and photographs of applepests and diseases. Note that biolog-ical information and controls that arelisted on these sites may be substan-tially different from those recom-mended in Wisconsin.Cornell University—

nysipm.cornell.edu/factsheets/treefruit

Penn State University—ssfruit.cas.psu.edu/PomeFruits.htm

Virginia Polytechnic Institute andState University—ento.vt.edu/Fruitfiles/VirginiaAppleSite.html

West Virginia University—caf.wvu.edu/kearneysville/wvufarm1.html

North Carolina State University:ipm.ncsu.edu/apple/contents.html

Sources of pest managementequipment and suppliesGreat Lakes IPM—

greatlakesipm.com800-235-0285

Gempler’s—gemplers.com800-382-8473

University of Wisconsin-Extension does not advocate thesesources over other sources of pestmanagement supplies.

A P P L E P E S T M A N A G E M E N T

References to pesticide products in thispublication are for your convenience andare not an endorsement of one productover other similar products. You areresponsible for using pesticides accordingto the manufacturer’s current label direc-tions. Follow directions exactly to protectthe environment and people from pesticideexposure. Failure to do so violates the law.

Copyright © 2006 by the Board of Regents of the University of Wisconsin System doing business as the division of CooperativeExtension of the University of Wisconsin-Extension. All rights reserved. Send copyright inquiries to: Cooperative ExtensionPublishing, 432 N. Lake St., Rm. 103, Madison, WI 53706.

Authors: Patty McManus is professor of plant pathology, Dan Mahr is professor of entomology, and Teryl Roper is professor of horti-culture, College of Agricultural and Life Sciences, University of Wisconsin-Madison and University of Wisconsin-Extension,Cooperative Extension. Produced by Cooperative Extension Publications, University of Wisconsin-Extension.

University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S. Department of Agriculture andWisconsin counties, publishes this information to further the purpose of the May 8 and June 30, 1914 Acts of Congress. An EEO/AAemployer, the University of Wisconsin-Extension, Cooperative Extension provides equal opportunities in employment and program-ming, including Title IX and Americans with Disabilities (ADA) requirements. If you need this information in an alternative format,contact Cooperative Extension Publishing or Equal Opportunity and Diversity Programs, University of Wisconsin-Extension,501 Extension Building, 432 N. Lake Street, Madison, WI 53706, diversity@uwex.edu, phone: 608-262-0277, fax: 608-262-8404,TTY: 711 Wisconsin Relay.

This publication is available from your Wisconsin county Extension office (www.uwex.edu/ces/county) or from CooperativeExtension Publishing. To order, call toll free: 877-WIS-PUBS (877-947-7827) or visit our web site at learningstore.uwex.edu.

A2179 Apple Pest Management for Home Gardeners R-01-2007