Organic Pears

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The National SustainableAgriculture Information Service,ATTRA (www.attra.ncat.org),was developed and is managedby the National Center forAppropriate Technology (NCAT).

The project is funded througha cooperative agreement withthe United States Departmentof Agricultures Rural Business-Cooperative Service. Visit theNCAT website (www.ncat.org/sarc_current.php) formore information onour other sustainableagriculture andenergy projects.

1-800-346-9140 www.attra.ncat.orgA project of the National Center for Appropriate Technology

By Guy K. Ames and

Holly Born

NCAT Agriculture

Specialists

Published April 2003

Updated May 2012

by Guy K. Ames

NCAT

IP167

Slot 36

Contents

Pears: Organic ProductionThis introduction to commercial organic pear production covers pear diseases, disease-resistant culti-

vars, rootstocks, insect and mite pests, and their treatment, Asian pears, and marketing. Two profles

of organic pear growers are included. Electronic and print resources are provided for further research.

Blakes Pride pear. Photo: Scott Bauer, courtesy of USDA

IntroductionIn much o the United States and with fre-

blight-resistant cultivars, pears may be the easi-est o the major tree ruits to produce organi-cally or with minimal spraying. Pear ertility

requirements are not highthey are adapted toa wide range of climates and soils, and they haveewer pest problems than other tree ruits.

Standard cultural considerationssuch as

pruning, planting, spacing, and thinningaregenerally the same or organic and conventionalgrowers. For this type o cultural inormation,

consult your county or state Cooperative Exten-sion Service and/or ind the inormation in

orcharding texts, articles, and websites (see theFurther Resources section at the end of this pub-lication). For general cultural inormation morespecifc to organic production (organic ertiliza-

tion, organic weed control, etc.), see ATTRAsTree Fruits: Organic Production Overview.

Pears have most o the same pest and diseaseproblems that apples have but usually to a con-siderably lesser degree. ATTR AsApples: OrganicProduction Guideidentifes pests and suggestsorganic remedies that are just as appropriate topears; thereore, most o these problems are notdiscussed urther in this publication. However,fre blight is considered in more depth becauseof its importance and prevalence on pears. Other

Introduction ......................1

Diseases ..............................2

Insect and Mite Pests .....7

Asian Pears .........................9

Economics andMarketing .........................11

References ...................... 13

AdditionalResources ........................ 13

Appendix......................... 14


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Page 2 ATTRA Pears: Organic Production

Related ATTRAPublications

www.attra.ncat.org

pests and diseases peculiar to or especially trou-

blesome to pears are also discussed.

In the last two to three decades, another type o

pear, the Asian pear, has joined the more amil-

iar European pears in American orchards and inthe American marketplace. Te similarities and

dierences between these two types o pears are

summarized in able 1.

Diseases

Fire BlightFire blight, caused by the bacterium Erwinia

amylovora, is the most serious and economically

damaging disease o pears. Occurring through-out the pears range, it is particularly trouble-

some in the humid eastern United States. Inec-

tion is triggered by heat and moisture and can

spread rapidlyeven within a matter o hours.

It can be transmitted by bees, aphids, psylla, or

other insects, and it can also be spread by blow-

ing wind and rain. Pruning can be another source

o inection. Aected branches wither and turn

black or brownish black, as i scorched (Figure 1).

Most branch tips, once inected, wilt rapidly,taking on the characteristic shape o a shep-herds crook. Te bacteria gain entry to the treethrough blossoms or lush new growth and, onceinside, begin to work toward the roots. I the

disease spreads unchecked to the trunk and

Table 1. Comparing a Pair o Pears

European pears Asian pears

Scientic names Pyrus communis Pyrus ussuriensisP. serotinaP. bretschneideri

Common cultivars Bartlett, Bosc, D'Anjou,Seckel, Magness, Maxine,

Moonglow, Comice

20th Century, Shinseiki, KoreanGiant, Shinko, Chojuro, Niitaka,

Clear Moon, Shin-Li, Tsu LiTexture and avor Buttery smooth and sweet Crisp. Flavors vary widely,

including bland, sweet, sweet-tart, pineapple-like, and more.

Color Green to yellow, thoughrussetted types are dullbronze, and there are a ewred types

Green, yellow to golden,russetted bronze, and manytypes with white lenticels (spots)

Shape Pyriorm (i.e., round & bulb-like on the calyx end,narrowing to a slender neckat stem end)

Most cultivars are round. Someare misshapenly round. A eware slightly pyriorm.

Harvest and postharvest Harvest beore ully ripe.Allow to ripen (cure) atroom temperature. Buyerusually does curing.

Allow to tree-ripen. Ready toconsume or sell.

Pests and diseases Same as or Asian (see text) Same as or European (see text)

Figure 1. Characteristic re blight symptoms on

shoots and leaves. Photo: Florida Division o Plant

Industry Archive, Florida Department o Agriculture

and Consumer Services

Tree Fruits: Organic

Production Overview

Postharvest Handling

o Fruits and

Vegetables

Farmscaping to

Enhance Biological

Control

Biointensive

Integrated Pest

Management (IPM)

Apples: Organic

Production Guide

Grapes: Organic

Production

Peaches: Organic

and Low-Spray

Production


3/16

Page 3ATTRAwww.attra.ncat.org

roots, it can kill the tree. Under the bark, thebacteria orm a canker where they will survivethe winter and inect more trees the next year.

Fire blight development is greatly avored by thepresence o young, succulent tissues, and there-ore cultural practices that avor only moderategrowth o trees are recommended. Tese includeusing only hal as much compost as or apples,

never using resh manure, and avoiding heavypopulations o clovers and other legumes aroundthe base o the tree. Likewise, heavy pruningcan promote lush, vigorous growth, so suchpruning should be avoided.

Choosing re-blight-resistant pear cultivars is agood start to managing re blight, but it is by nomeans a panacea (see the Appendix, Fire Blight,Disease Resistance, and the Disease riangle).Relative resistance to the disease is sometimesinormally measured by the extent o visible

inection to the age o wood. For instance, Kie-er is commonly reerred to as resistant becausethe disease rarely proceeds beyond one-year-oldwood; you might see a lot o blight on Kieer ina bad inection year, but rarely will such inec-tion move beyond young wood and threatenthe trees lie. A highly-resistant cultivar, likeKoyama, might show a ew blighted blossoms,but it rarely suers inection past that point (seeFigure 2). Conversely, a highly susceptible culti-var like Bartlett, under disease-conducive con-ditions, could incur an inection that could run

rom new growth to roots and kill a mature treein a single year.

Tere are several European-type pears with acomparatively high level o re blight resistance(including Ayres, Blakes Pride, Harvest Queen,Honeysweet, Magness, Maxine, Moonglow,Potomac, yson, and Warren) that are adaptedto most o the contiguous United States. Clapps,Bartlett, Comice, Anjou, Bosc, and most othercultivars that are not expressly described as reblight resistant in a nursery catalog should be

considered susceptible and grown organicallyonly in the semi-arid production areas o theWest; even then they will probably require pro-tection (see below).

Asian-pear cultivars also vary in their resistanceto re blight. Shinko has a high level o resis-tance, while Korean Giant, Ya Li, Niitaka, ClearMoon, Shinsei, and Seuri are among the mod-erately resistant varieties. Shinseiki has beenrated as resistant by Kentucky researchers

and susceptible by Alabama A&M research-ers (Jones and Fackler, 1995). Shin Li is listed asresistant in some literature, but experience withheavy re blight pressure under humid Arkansasconditions indicates that it is quite susceptible.Tese variations in resistance ratings can usuallybe explained by dierences among the grow-ing sites, e.g., conditions in Arkansas are muchmore conducive to re blight development than

they are in New England or Oregon. It may besome time beore all Asian-pear cultivars, beingrelatively new in the United States, are wellclassied in terms o blight resistance.

Preventing inection is the next key to re blightcontrol. Sprays o agricultural-grade antibiotics,applied at early bloom to prevent inection, havebeen the standard commercial control since the1950s, but they are scheduled to be phased outor certied organic use in 2014 due to concernsabout the buildup o antibiotic-resistant strainso bacteria. University researchers and the pearand apple industries have been working to ndviable substitutes or these antibiotics, and theirdiligence is paying o with the development oseveral biocontrol products.

In general, these biocontrols work similarly toone another. hey are non-pathogenic com-petitors with E. amylovoraand as such do notdirectly kill propagules oE. amylovora; rather,they occupy the same sites that E. amylovorawould, provided they get there rst. Tereore,in order to be eective, these should be appliedto newly opening owers (multiple applications

Figure 2. Blossom blight phase o re blight on Koyama, a cultivar rated as resis-

tant because the blight will generally not progress past the blossoms into older

wood. Photo: Guy Ames, NCAT


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will probably be necessary). Since they do notdirectly challenge the metabolism oE. amylov-ora, there is little risk o the pathogen buildingresistance to them.

Currently, according to Oregon State research(Johnson, 2012), the best control seems to bethe yeastAureobasidium pullulans, packaged andsold as Blossom Protect, a product o West-

bridge Agricultural Products (www.westbridge.com). Over a our-year period, Dr. Ken Johnsoncompared Blossom Protect to BlightBan (Pseu-domonas fourescens, see below) and BloomtimeBiological (Pantoea agglomerans), and oundBlossom Protect to be the best o the three bio-logicals; it provided very good protection romre blight when properly applied (ollowing labeldirections). Blossom Protect has already receivedapproval or use on certied organic arms by theWashington State Department o Agriculture,and Westbridge Agricultural Products is seek-

ing approval rom the Organic Materials ReviewInstitute (OMRI). Check the OMRI websitewww.omri.org or the current status.

Combinations o these products may be evenmore protective. In eld trials in Oregon, John-son ound that a regime o Bloomtime Biologicalollowed by Blossom Protect provided re blightcontrol equivalent to protection rom antibiotics.Johnson ound that the Bloomtime Biologicalpreerentially colonized and protected the owerstigma, while the Blossom Protect seemed supe-

rior in protecting the nectary.

BlightBan is a ormulation o the bacterium Pseu-domonas fuorescensstrain A506. P. fuorescensstrain A506 is resistant to streptomycin; in act,research indicates that re blight suppression isbest when streptomycin and BlightBan are com-bined. BlightBan is marketed by J. R. SimplotCompany/Plant Health echnologies (800-535-9101) and is OMRI approved.

Not surprisingly, these biological control agentsare not showing the same ecacy in the eastern

United States where disease pressure is higher (seethe Appendix on Disease riangle). Sundin etal. (2009) tested BlightBan, Bloomtime, and Ser-enade Max (Bacillus subtilis) over seven years inMichigan, Virginia, and New York. Tese mate-rials exhibited low ecacy and high year-to-year and location-to-location variability, lead-ing researchers to conclude that the prospectsor biological control o re blight in the easternUnited States are currently not high.

OxiDate is a hydrogen dioxide product that isOMRI-approved and registered or re blightcontrol but doesnt seem to be eective, at leastunder eastern conditions, and it can cause severeruit russetting. According to the 2011 New Eng-land Tree Fruit Management Guide, Controlledinoculation trials indicate no signicant eect oOxiDate on re blight inection . (Cooley etal., 2011).

Bordeaux mix (copper sulate and lime) and othercopper ormulations sprayed at green-tip stageare organic options that provide some protectionrom re blight inection. For best results, theseormulations should be applied to all the trees ina block, not only the blight-susceptible cultivars(Steiner, 1995). Copper treatments can cause ruitscarring and are phytotoxic to some cultivars, socareul application is important.

Ken Johnsons Oregon research has identied

new copper products (relatively small amounts ocopper in organic acids, e.g., Phyton 27 AG andGowan GWN9979) as highly eective againstre blight and not a cause o russetting, but theyare not yet approved or organic production.

A computer sotware program called Maryblytis available to help in timing antibiotic sprays ortheir most efcient application against re blight.Te grower enters daily minimum and maxi-mum temperatures, rainall, and stage o blossomdevelopment, and the program predicts inec-tion events and symptom development or mostphases o re blight. Further inormation on theprogram is available at the USDAs AppalachianFruit Research Station website, www.ars.usda.gov/naa/ars. In the Pacic Northwest, the simi-lar Cougarblite Model (www.ncw.wsu.edu/tree-ruit/models.htm) is more oten used to help timespraying, and elsewhere other degree-hour modelsrom local sources may be more appropriate.

Once re-blight inection has occurred, there isno spray or other treatment, beyond quickly cut-ting out newly inected limbs, that will mini-

mize damage. However, inection has almostcertainly extended beyond what the growersees; thereore, it is all too easy to spread thedisease by trying to prune it out during thegrowing season. I you do cut during the grow-ing season, remove all blighted twigs, branches,and cankers at least 8 inchessome sourcesrecommend 12below the last point o vis-ible inection and burn them. Ater each cut,the shears can be sterilized in a strong bleach

Once re-

blight

inection

has occurred, there

is no spray or other

treatment, beyond

quickly cutting

out newly inected

limbs, that will

minimize damage.
http://www.ars.usda.gov/naa/afrshttp://www.ars.usda.gov/naa/afrshttp://www.ncw.wsu.edu/treefruit/models.htmhttp://www.ncw.wsu.edu/treefruit/models.htmhttp://www.ncw.wsu.edu/treefruit/models.htmhttp://www.ncw.wsu.edu/treefruit/models.htmhttp://www.ncw.wsu.edu/treefruit/models.htmhttp://www.ars.usda.gov/naa/afrshttp://www.ars.usda.gov/naa/afrs


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or Lysol solution (one part household bleach orLysol to our parts water) to help avoid trans-mitting the disease rom one branch to another,although there is some disagreement about theeectiveness o disinection. Lysol is less corro-sive than bleach to the metal parts o the prun-ers. Some have ound it more convenient to usea spray can o Lysol disinectant carried in anapron rather than a plastic holster or glass jarwith a liquid solution.

During the winter, when the temperature ren-ders the bacteria inactive, pruning out ire-blight-inected wood can proceed without steril-ization o pruning tools and need not extend asar below the visible canker.

Pseudomonas Blight (BlossomBlast)Another bacterial disease, blossom blast (causal

organism: Pseudomonas syringae, not to be con-used with Pseudomonas fuorescensdiscussedabove), may afict pears, usually as a blossomblight resulting in reduced ruit set. It can alsocause twig dieback and bark cankers and maylead to severe wood damage o Asian-pear cul-tivars in particular (see the Boullioun GrowerProle or more inormation on pseudomonasand Asian pears). Because the presence o blos-som-blast bacteria allows ice crystals to orm athigher-than-normal temperatures, the disease

increases the incidence o reeze damage dur-ing cold, wet weather. Asian pears are especiallyaected because their early bloom makes themmore susceptible to rost injury (Elkins, 2001).Among Asian-pear cultivars, Shinko and Ya Liare moderately resistant to P. syringae.

Controlling this disease is dicult because itsoccurrence is widespread on many plant spe-cies and not easily predicted; once symptomsappear, control eorts are too late. Protectingorchards rom rost damage can limit injury.An early applicat ion o BlightBan A506 canhelp reduce rost-damage potential by exclud-ing the ice-nucleating bacteria. In Caliornia,the application o xed copper at the green-tipstage ollowed by streptomycin at early bloomhas provided reasonable control. Tis treatmenthas also been used in Oregon and Washington,where cool, wet weather makes blossom blast aparticular problem in pear production. Strep-tomycin or terramycin applied at early bloom

to control re blight also helps to control blos-

som blast, but sprays timed or re blight con-

trol cannot be assumed to control blossom blastbecause P. syringaeis avored by cool, wet con-

ditions while E. amylovoraprolierates in warm,wet conditions. In other words, predictive mod-els or re blight could easily miss an inection

period or blossom blast. Tere are no predictive

models or blossom blast, so the prudent growerwith a history o blossom blast in the orchardwil l apply copper at green tip and ollow up

with BlightBan or streptomycin at early bloom

regardless o what re blight predictive models

might indicate.

Pear ScabPear scab (Venturia pirina, Figure 3), a ungal

disease closely related to apple scab, is neither

as common nor as economically important on

pears as apple scab is on apples. Nevertheless,

it can cause economic damage by marring the

appearance o the ruit. Pear scab causes lesions

on leaves, shoots, and ruit, andunlike apple

scabinects twigs, where it can overwin-ter. Pear cultivars dier in their susceptibil-

ity to scab. Organic control is identical to that

or apple scab (Jones and Sutton, 1996), usu-

ally consisting o treatment with sulur, lime

sulur, or Bordeaux mixture. See ARAs

Apples: Organic Production Guide or details,

including the use o the Mills able to predictinection periods.

Figure 3. Pear scab. Photo: Howard F. Schwartz, Colorado State University


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Pear DeclineHistorically, pear decline was a devastating dis-ease. Accidentally brought to the United Statesrom Europe in the 1940s, pear decline wasresponsible or the deaths o well over a milliontrees in western commercial pear-growing dis-tricts in the 1950s and 1960s (Agrios, 1997).

he phytoplasma organism that causes pear

decline is vectored by pear psyllae (see the sec-tion on Insect and Mite Pests), and ull expres-sion o the disease depends greatly on rootstocksusceptibility. It can also be spread by gratingand budding with inected propagation wood.Inected trees usually exhibit a slow decline invigor and ruit production, cupped leaves, andearly all deoliation. Interestingly, the phyto-plasma does not appear to increase in inectedtrees but does increase in the psyllae; conse-quently, heavy and continuous eeding is most

likely to result in symptoms, and, conversely,good pear-psylla control usually results in dis-ease remission even when rootstocks are highlysusceptible (Elkins et al., 2001).

With this understanding and subsequent con-version to resistant rootstocks, as well as bet-ter psylla control, pear decline is now itsel indecline. Susceptible rootstocks include seedlingsoP. serotina, P. ussuriensis, and P. calleryana.olerant or resistant rootstocks include the OHXF series, Bartlett seedling, and P. betulaeolia.Other control methods include keeping the treein good vigor with proper weed control, watermanagement, and ertilization.

Other Diseaseswo oliar diseases, abraea lea spot (Fabraeamaculata) and mycosphaerella lea spot (Myco-sphaerella pyri), are usually no problem insprayed orchards but can reach damaging lev-els in unsprayed ones (Jones and Sutton, 1996).Susceptible cultivars, which include nearly allEuropean pears, can be deoliated, resulting inreduced buds and dwared ori the ruit itselis inectedunmarketable ruit. Sprays or pearscab, such as Bordeaux mixture, will generallycontrol these two maladies as well. Also, Sur-round, a kaolin-clay-based insect repellant, isregistered and labeled or suppression o abraealea spot.

The Rootstock Connection

Choice o pear rootstock can be important in controlling re blight as well

as or actors such as tree size, soil adaptability, tolerance to pear decline,

and cold hardiness. For decades, almost all pear varieties were grated

onto Bartlett seedlings, probably because Bartlett seeds were so easily

obtained rom the pear canning industry. Just about the only other root-

stock choice or years was quince, which resulted in a dwared tree that

oten struggled to survive and also exhibited grat incompatibility with

many cultivars. Bartlett seedling rootstock produced a large tree, wasnot adapted to all soil types, and was subject to re-blight inection and

pear decline, a disease that was a problem in many western production

areas. Bartlett was not the ideal rootstock that the pear industry desired.

In 1915, Oregon researcher Dr. F.C. Reimer began a long-term rootstock

search and breeding efort that started to address these problems and is

still producing results. He went to China and brought back seeds o sev-

eral Pyrus species. He also crossed a European-type cultivar, Old Home,

with a chance seedling which he dubbed Farmingdale, both o which

exhibited resistance to reblight, and the selected progeny o which are

now reerred to as the OH X F rootstocks. Washington State University

and Oregon State University research, as well as grower experience, con-

tinue to add to our knowledge o pear rootstocks.Several o these OH X F clonal (reproduced asexually as opposed to sexu-

ally reproduced seedlings) rootstocks have emerged as dependable and

many more as promising. Tree size control, as well as regional diferences

in soils, climate, and disease incidence can be now be addressed, some-

what, with diferent rootstocks. The commercial pear industry centered

in the Pacic Northwest appears to be best served by the semi-dwarng

OH X F 40, 69, and 87, with 87 showing consistently best results in grower

trials (http://county.wsu.edu/chelan-douglas/agriculture/treeruit/Pages/

Pear_Rootstock_Research_Project.aspx).

Among the seedling rootstocks, P. calleryana has proven to be a very

good re-blight-resistant seedling rootstock or the South and upper

South. It can tolerate wet soils, drought, acid soils, and even clay soils. Itis, however, not very cold hardy and produces a large tree.

P. betulaefolia is another rootstock that has specic desirable qualities:

tolerant o wet and droughty soils, very resistant to pear decline, and cold

hardy. Like virtually all seedlings other than the size-controlling clonal

rootstocks, it produces a large tree. Betch, as growers oten call it, seems

particularly good or Asian pears. Jef Boullioun (see Grower Prole),

a commercial-scale, organic Asian-pear grower in Washington, ound

that Asians on OH X F rootstocks were too susceptible to the ravages o

pseudomonas and replaced them all with betch, which continues to

give him good production. Through pruning and training he is able to

keep his Asians on betch to about 12 to 13 eet in height.

Bartlett seedling is still widely used and has some desirable qualities like

drought tolerance. Nevertheless, i Bartlett is used as an understock, the

grower should be aware that a re-blight inection could occur. This prob-

lem can be mitigated by grating to a re-blight-resistant cultivar, but i

the rootstock is allowed to sucker, those tender shoots can be inected

and the inection spread to the roots.


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Insect and Mite PestsMany o the same pests that aect apples also

prey on pears, although usually to a lesser

degree, with codling moth being a good exam-

ple. More inormation on dealing with these

pests can be ound in ARAsApples: Organic

Production Guide. Some o the pests that par-

ticularly aect pears are discussed below.

Proper pest identication and orchard scoutingare key to implementing successul IPM pro-

grams. ARAs Biointensive Integrated Pest

Management (IPM) publication provides addi-

tional inormation.

Pear Psylla

Te pear psylla (Cacopsylla pyricola), an aphid-

like insect whose only host is the pear, is thecrops most signiicant insect pest. In con-

junction with re blight, pear psylla is largely

responsible or declining eastern pear produc-

tion. he honeydew let by the psylla dam-

ages the ruit by supporting growth o sooty

mold and causing a black russeting; these two

eects account or most o the economic dam-

age caused by the psylla. It is also an important

vector o re blight and pear decline disease and

can weaken trees in areas o heavy inection.

Although the psylla develops resistance to insec-ticides, it can usually be controlled either with

dormant oil sprays or with sulur sprays (but

not a combination o the two, which damages

plants). Insecticidal soap can reduce active pop-

ulations during the growing season. Fortunately,

the recently introduced Surround kaolin-clay-

based insect repellant is eective against pear

psylla. In act, use o Surround or pear psylla

control has made organic pear production viable

or the rst time in states like Michigan (Anon.,2002). Te psylla also has a number o naturalenemies such as predatory ies, minute piratebugs, and lacewing larvae. In organic orchards.parasites and predators can help control psyllabelow economically damaging levels, especiallywhen combined with a program o oil treat-ments (Elkins et al., 2001).

True BugsStink bugs, tarnished plant bug, and other truebugs (insects in the order Hemiptera) will read-ily eed on pears throughout the growing season.Early eeding damage may result in a pucker ordimple in the ruit. Mid- and late-season eed-ing oten results in the development o so-calledstone cells immediately beneath the eedingsite. Tese stone cells are very hard and can seri-ously compromise the marketability o aectedruit.

Some ruit and nut growers reduce true-bugdamage by maintaining unmown leguminoustrap crops (clovers, vetches, peas, etc.) near theorchard (Anon., 1999). Unmown areas and covercrops can also serve as habitat or predator insects;or more inormation, see the ARA publica-tion Farmscaping to Enhance Biological Control.

Surround is labeled or suppression o stink-bugs and lygus bugs in pears. Also, some o thebotanical insecticides derived rom the seeds othe neem tree are eective against true bugs onruit crops. For example, OMRI-approved Aza-Direct (www.aza-direct.com) is labeled oruse on all pome ruits or the control o wee-vils, thrips, true bugs, leahoppers, aphids, lea-rollers, cutworms, ies, and mites.

MitesIn high enough numbers, pearlea blister mites(Phytoptus pyri) and pear rust mites (Epitrimeruspyri) can reduce the photosynthetic efciency oleaves and cause russeting on ruit. Both specieswil l likely be more troublesome in dusty con-ditions, as the dust intereres with their natu-ral predators. Tese predatorsincluding greenlacewings, predatory mites, and various specieso ladybird beetles, as well as bigeyed bugs, min-ute pirate bugs, and predatory thripswill usu-ally control mite outbreaks i the predators arenot disrupted by dust or pesticides. Orchardmonitoring can help establish whether adequatenumbers o benecial insects are present. I they

Figure 4. Damage rom pear psylla. Photo: Whitney

Cranshaw, Colorado State University

U

nmown

areas

andcover crops can also

serve as habitat or

predator insects; or

more inormation;

see the ATTRA

publication

Farmscaping to

Enhance Biological

Control.


8/16


are not, horticultural oils sprayed during thedormant season can suppress mite eggs throughsuocation. Neither horticultural oils nor othermaterials approved or organic production pro-vide economic control o damaging populations.

Another pest that contributes to poor yields andsmaller ruit is the spider mite. Dormant hor-ticultural oils and insecticidal soaps can both

help control spider mite outbreaks. Neem-basedbiological insecticides are also labeled or con-trolling mites on pears. European-pear cultivarsare more sensitive to mite eeding than Asianpears, and any pear that is drought-stressed willbe more susceptible to mite damage (University

o Caliornia Statewide Integrated Pest Manage-ment Project, 1991).

Other InsectsOther insect pests that may aect pears includecodling moth, apple maggot, scale, and plumcurculio. Tese insects are covered in ARAsApples: Organic Production Guide publication.

Te pear slug (actually a sawy larva) causeslea damage; it can be controlled with a orce-ul stream o water, soap, or wood ashes. Telearoller complexincluding tuted apple budmoth, variegated learoller, and redbanded lea-rollersrepresents another potential, but com-

Grower Prole:

Peshastin Creek Growers Association

(Excerpted by permission from Renewing the Countryside: Washington, by Ingrid Dankmeyer , John Harrington, and Jim Anderson,

published in 2005 by Sustainable Northwest, 813 SW Alder Street, Suite 500, Portland, OR 97205, www.sustainablenorthwest.org)

Central Washingtons Wenatchee Valley is an excellent place to grow pears and apples, with warm, dry days and cool nights.

Around Peshastin Creek, a tributary o the Wenatchee River, a handul o amily orchardists are carrying on the work started

by their grandathers and great-grandathers. But this generation o pear growers is experimenting with gentler pest man-

agement strategiesstrategies that seem to be working.

In 2000, Dr. John Dunley, Washington State University tree ruit entomologist, set out to build on the codling moth mating

disruption success story [see ATTRAsApples: Organic Production Guide or more inormation on codling moth mating disrup-

tion]. He wanted to complement the mating disruption approach with strategies to increase the populations o benecial

insects that eat codling moths and other pests.

John explains, A lot o the natural enemiesor good bugscome rom the surrounding natural vegetation, so i everyone

went to a sot (low pesticide) program, we could create avenues or movement o natural enemies over an entire area with-

out any pesticide barriers. When high levels o pesticides are used, both the bad and the good bugs are killed. John was still

developing his idea when the Peshastin Creek Growers Association got wind o it. Says John, I was going to take another year

to urther develop the theory and the economics o it when these guys heard about it and gave me a call.

In the beginning there was a lot o concern about whether or not there would be economic damage in the orchards due to

pests coming in and harming crops to the extent that they couldnt be sold. Peshastin Creek grower Dennis Nicholson says,

In some situations that did happen because people were not on top o things. That has been part o the learning curve: you

have to arm a little diferently in a sot pesticide program than you do in a conventional program.

Now hal o the 310 acres managed by the Peshastin Creek Growers is organic and the rest is managed with a sot program.

Says Dennis, Its gotten to the point where the sot program is very efective. The spray I am currently using or the sot block

is exactly the same spray as I am using or the organic blocks. The only signicant diference between the organic and the

sot block is that we are able to use herbicides, rodenticides, and ertilizers.

The Peshastin Creek Growers market collectively under the Gently Grown label and received the Food Alliance sustainable

agriculture seal o approval in 2002. Finding markets or their unique product that is not quite organic and not conventional

has been a bit o a challenge. Says Nicholson, Last year or the rst time we ound a customer in Caliornia who was willing

to pay us a premium or the Gently Grown label, so there are niches out there that are willing to pay or a pesticide-ree or

low-pesticide ruit.

One o the things that might be diferent about our group is that we all started out as conventional armers, and our athers

were conventional armers, adds Dennis. We had to come into the idea o a sot pesticide or organic program rom our ear

o insect resistance, our ear o polluting water, our ear o regulation, plus our motivation to raise a superior product and do it

in a kinder, gentler way. Thats where the Gently Grown label comes rom; we are trying a more gentle with nature approach

to growing our product, and basing our inputs on need.


9/16


paratively minor, pear pest problem. Matingdisruption tools that are eective or some lea-

rollers are being developed. In addition, thereare biological insecticides labeled or controlo leahoppers, aphids, and learollers, among

other pests.

Asian Pears

Because they are relatively new to much o theUnited States, Asian pears deserve some addi-tional comment. A crisp, juicy ruit, Asianpears are also known as Oriental pears, nashi,

sand pears, apple pears, or salad pears. Temore than 1,000 varieties o Asian pear rangewidely in shape, color, and taste. Only about a

dozen varieties are commonly grown in U.S.commercial orchards.

Asian pears are slightly less cold-hardy than Euro-pean types; they may suer tissue damage at tem-

peratures below -10F but are generally hardy to-20F, making them best adapted to USDA planthardiness zones 5 to 9. Most Asian pears bloom

slightly earlier than their European counterparts

and may lose some blooms or buds to reezing inareas with a highly variable spring climate.

Culture o Asian pears is similar to that o Euro-pean types but not identical. One signicant

dierence is the common tendency or manyo the Asian types to set too heavy a ruit crop,

which requires hand thinning o young ruitsoon ater bloom. Shinko, a popular cultivarbecause o its high ruit quality and re blightresistance, is especially prone to this problem(Figure 5). I not properly thinned, Shinko andany other heavy-bearing Asian-pear cultivarswill not be able to mature such a load success-

ully. Fruit size and quality will suer. On theother hand, thinning to promote ruit size mayresult in reduced yield per acre compared toEuropean-pear varieties.

Another dierence between Asian and Euro-pean pears is that Asian pears ripen on thetreethey do not have to be picked and thencured like European pears. Tis is an advan-tage or most growers, especially growers whoare retailing direct to consumers. Te ruit canbe tree-ripened and is ready to eat when pickedor can be held in cold storage. Growers do nothave to educate buyers about curing, as theymight with European pears.

It is important to note that the delicate ruito many Asian-pear varieties must be careullyhandled during and ater harvest to minimizebruising, punctures, and roller marks. heskin o Asian pears discolors quickly ollowingrough handling, making careul picking andpackaging a necessity and mechanical handlingrisky. o prevent damage to Asian pears, it maybe best to pack them into padded boxes or traysin the eld where they are picked.

Chojuro Asian pear. Photo: Jerry A. Payne, USDA Agri-

cultural Research Service

Figure 5. Heavy bloom on Shinko pear will require blossom or ruit thinning to pre-

vent the tree rom over-cropping and to maintain ruit size and quality. Photo: Guy

Ames, NCAT


10/16


Grower Prole:

Organic Asian Pear Growers Jef and Kristine Boullioun

Though Busy Bee Orchard co-owner Jef Boullioun still has 20 acres o apples and 26 acres o Bosc

and Super Red European pears, it s the 9 acres o organically certied Asian pears o which he seems

proud. When other early adopters were giving up on Asian varieties, Boullioun had gured out that

each variety had to be treated according to its individual traits. Each Asian pear is grown difer-

ently and handled diferently, Boullioun said. Thats our distinct advantage over other Asian pearproducers.

Boullioun said the special treatment

starts long beore harvest. Each Asian

pear tree is marked with colored paint to

make sure workers at Busy Bee Orchards

know the diference between the 11 vari-

eties. Special pruning practices are used

both or winter and summer pruning

because some varieties need heavy trim-

ming while others need less. The same

concept applies to thinning o the ruit,

and, o course, each variety has its own

window or optimum quality at harvest.

The Boulliouns bought 58 acres near

Oroville, Washington (near the Cana-

dian border), in 1981 and planted it all to

Red and Golden Delicious apples. Gen-

erally poor prices or apples prompted a

gradual transition to pears, beginning in

1987. Busy Bee Orchard became organi-

cally certied in 1999 primarily or eco-nomic reasons. But ater growing organi-

cally or over 10 years now, we hope that

we dont ever have to arm convention-

ally again. Our workers like the act that

we dont spray anything harmul to them and re-entry on most sprays is only a ew hours. We only

target the pest and save the benecials.

There are so many great organic pesticides out now that we dont have much o a problem with

insects. The worst problem is weed control, as there arent any really efective organic herbicides.

We do a lot o hand weeding around the young trees, use a string trimmer around the older trees

and rotovate. Birds can also be a real problem when the ruit ripens. We use pretty much everyrepellent available: cannons, squawkers, balloons, noise guns, ash tape, GO. The birds especially

love the Asian [pears], and we can lose hundreds o dollars a day to bird pecks.

Pseudomonas is their most serious disease problem. Switching to P. betulaefolia rootstocks helped,

but their main control technique is copper sprays at early and ull bloom.

They market their organically certied pears through Stemilt brokers, and the bulk o their crop

ends up in Whole Foods Market stores. Says Jef proudly, Were very particular about what goes in

the box, especially since that box has our name on it.

Busy Bee Orchards Asian pear packing line. Note the

socks on the individual ruit, reecting the Boulliouns

concern or ruit quality. Photo: Jef Boullioun


11/16


More inormation on Asian pears can be oundin the sources provided in the Reerences andFurther Resources sections.

Economics and MarketingAccording to USDAs 2008 Organic Produc-tion Survey, the United States had 257 certi-ed organic arms that produced 21,684 tons o

pears worth $16 million (Geisler, 2011).At one time, pears were grown commercially ona large scale throughout the United States. How-ever, because o the prevalence o re blight inthe humid eastern and southern states, most pearproduction has been relocated to the drier areas othe Pacic Northwest. According to the USDA,97% o the pears produced in the U.S. are grownin Washington, Oregon, and Northern Calior-nia (Foreign Agricultural Service, 2002).

In general, pear prices tend to uctuate based

on crop sizewhich can be highly variable onaccount o weather and ruit set ratesandon the number o growers producing pears ina given year. Fluctuation in the organic marketis also based on these actors, and the premiumthat organic growers can expect to receive ortheir product is unpredictable at best.

Te market or pears is weaker than it could

be, largely because o consumers unamiliar-

ity with the dierent types o pears and how to

use them. One survey showed that Bartletts and

winter pears were consumed by no more than

hal o Americas households, and then only

occasionally (Pear Bureau Northwest, 2012).

A market study unded by the Pear Bureau

showed that only three out o 10 people havetried dAnjou pears, and two out o 10 have tried

Boscs. One o the obstacles limiting pear con-

sumption is that many consumers do not know

how to ripen them. Providing inormation on

ripening may help increase sales (though the

Pear Bureau study also ound that most people

preerred to buy pears already ripened). Many

pear purchases are impulse buys, so appearance

is critical. Rough handling causes brown marks

on the skin that may not appear until the ruit

has begun to ripen, and these will decrease cus-

tomer appeal, so pears should be handled gently.

he market or Asian pears is mixed. Until

1995 or so, the wholesale market or Asian pears

was quite open and prices were high, particu-

larly on the West Coast and in cities with large

Asian-American populations. But Asian pears

have been heavily planted in Caliornia or more

than 20 years, and those orchards are now mature

and bearing, more than meeting local demand

and causing price drops in some areas. Addition-

ally, China has become the world export leaderor pears, producing 15 million tons in 2010 and

depressing wholesale market prices or domestic

producers (Foreign Agricultural Service, 2011).

On the other hand, outside o Caliornia, Asian-

pear growers who direct-market to a retail clien-

teleespecially a local Asian-American popu-

lationreport brisk sales and good prices rom

locations across the country. Oering taste sam-

pling o ruit, where practical and allowed by

local health regulations, is probably a good idea

or building markets, since so many Americansare still unamiliar with Asian pears.

Asian pears are breaking out o their niche to

join the mainstream market and may represent

an opportunity or producers as market aware-

ness and demand continue to grow.

Conerence pear. Photo: Courtesy USDA/ARS

he

market

or pearsis weaker than it

could be, largely

because o

consumers

unamiliarity with

the diferent types

o pears and how to

use them.


12/16


Postscript: Pears in the Humid SouthThe Authors Experience

I have been a lousy pear orchardist, but I think and hope that my aults might lead to the benet o others. In 1990-1992, I

planted 120 pear trees as an adjunct enterprise to my larger apple orchard. I planted a lot o cultivars, both European and

Asian, all with some claim to re-blight resistance, on several diferent rootstocks in a slightly acid, well-drained, sandy loam

soil with a red clay subsoil.

Fire blight soon became my teacher and Darwinian judge o the weak. I learned rst-

hand that the resistance ratings generated rom research in Caliornia or New England

meant very little in the South, where the intense heat and humidity skewed the envi-

ronment to the avor oErwinia amylovora (see the appendix on the Disease Triangle

or more details). I probably lost 25% or more o my trees in the rst three to our years.

And I never sprayed antibiotics; my only control eforts were aimed at cutting out strikes

(inected wood) during dormancy.

Still, I had lots o ruit rom Magness, Maxine, Shinko, Korean Giant, and a smattering

o a ew other varieties, and what pears I took to the Fayetteville Farmers Market sold

easily and quickly. The Asian pears, especially, were cosmetically near-perect and very

easy to sell.

More importantly, compared to the apples and excluding re blight, the pears had prac-

tically no pest problems at all: no trunk borers, no codling moth, no plum curculio, no

summer rots, and no sooty blotch. All these were serious problems in the apples, and

I have to wonder i someespecially the codling mothwould have been more o aproblem i the apples hadnt been so close to possibly lure them away rom the pears.

Other than re blight, the only signicant pest problem Ive had on pears has been

dimples on the ruit rom early-season eeding by tarnished plant bugs and stink bugs.

In 2000, I essentially abandoned the pear orchard. I did not prune. I did not water. Once

or twice a year Id run my riding lawnmower through it. I let my neighbors run their

sheep in it. Fire blight continued its lessons: Chojuro, which at rst seemed resistant,

began to succumb to the disease in a series o years with long, wet springs, and Shin-

Li (one o my early avorites or its ginger-vanilla avor) was totally wiped out. Also, in

the decade 2000-2010, the weaker rootstocks were pretty much eliminated by virtue

o my neglect.

So, whats let ater 10 years o neglect, heat, humidity, disease, ice storm, drought,and ood? The rootstock that survived best wasPyrus calleryana (the species the now-

notorious Bradord ornamental pear comes rom). The surviving Asian and European

cultivars (roughly in order o their health and productivity): Shinko, Niitaka, Korean

Giant, Maxine, Magness, Clear Moon, and Koyama. Surviving but poor in either qual-

ity, yield, or disease resistance were: Kiefer, Warren, Seckel, Chojuro, Harrow Delight,

Moonglow, Harvest Queen, Potomac, and Bartlett seedlings as rootstocks. Total losers

or me: OH X F 333 rootstock and three Asian types with great avor but too suscep-

tible to re blightShin-Li, Hosui, and Shinseiki. One other, Erishinge, I couldnt even

get to live long enough to ruit!

In several instances where re blight killed the cultivar, the P. calleryana roots survived

and sent up vigorous, blight-ree shoots. Now that I have resumed care o the pears, I

have budded some o these shoots to blight-resistant cultivars (see Figures 6a and 6b).In this case, I let the blighted stump to dramatize the relative resistance and suscep-

tibility o the cultivars and root. With the roots already established, by the end o the

growing season the tree will probably be ve to six eet tall and branched.

I lay no claim to the scientic method in these comments. I did not try to replicate

my experiences (please, no!), and treatment sizes were small (i.e, three o one vari-

ety, our o another). And, hopeully, my conditionspoor soil, southern climate, and

neglectwill not be yours. These are just my observations. Make o them what you

will. May my losses be your gains!

Figure 6a. A new blight-ree shoot

resulting rom budding blight-resistant

cultivar Niitaka onto a healthy root

sprout. The original tree, stump remain-

ing, was killed to the ground by re

blight. The P. calleryana roots are highly

blight-resistant. Photo: Guy Ames, NCAT

Figure 6b. Close-up o the bud described

in Figure 6a. Photo: Guy Ames, NC AT-

killed to the ground by re blight. The

P. calleryana roots are highly blight-

resistant. Photo: Guy Ames, NCAT


13/16


ReerencesAgrios, G. 1978. Plant Pathology. Academic Press, NewYork, NY. p. 457-463.

Anon. 2002. Organic pears are a viable opportunity orMichigan growers. IPM Report. Spring. p. 1.

Anon. 1999. Pea patch diverts stinkbugs. Common Ground.Autumn. p. 4.

Cooley, Dan, et al. 2011. 2011 ree Fruit ManagementGuide. Pesticide Management Education Program, CornellUniversity, Comstock Hall, Ithaca, NY 14853-2601. p. 5.

Elkins, R.B., R. A. Van Steenwyk, L. G. Varela, and C.Pickel. 2001. UC Pest Management Guidelines: Pear Psylla.www.ipm.ucdavis.edu/PMG/r603301111.html

Foreign Agricultural Service. 2002. Te U.S. Pear Indus-try: Situation, rends, and Outlooks. FAS Online. www.as.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pd

Foreign Agricultural Service. 2008. 2007/2008 Global Pears.

FAS Online. www.as.usda.gov/htp/2008_Pears_Article.pdForeign Agricultural Service. 2011. Fresh Deciduous Fruit:World Markets and rade. FAS Online. http://www.as.usda.gov/htp/2011_Fruit.pd

Geisler, Malinda. 2011. Pears. Ag Marketing Resource Cen-ter, Iowa State University. www.agmrc.org/commodities__products/ruits/pears/

Johnson, Ken. 2012. Webinar: Fire Blight Control inOrganic Pome Fruit Systems Under the Proposed Non-antibiotic Standard. March 13. www.extension.org/pages/62448/re-blight-control-in-organic-pome-ruit-sys-

tems-under-the-proposed-non-antibiotic-standardJones, Alan, and urner B. Sutton. 1996. Diseases o reeFruits in the East. NCR 45. Michigan State University, EastLansing, MI. p. 22-23.

Jones, erry, and Ed Fackler. 1995. Asian pearsA past &uture in Kentucky. Pomona. Fall. p. 31-35.

Pear Bureau Northwest4382 SE International Way, Ste. AMilwaukee, OR 97222-4635www.usapears.com503-652-9720

Pest Management Guidelines: Pear Psylla. www.ipm.ucda-vis.edu/PMG/r603301111.html

Steiner, Paul W. 1995. Maryblyt beats re blight. AmericanFruit Grower. February. p. 30-31.

Sundin, G.W., N.A. Werner, K.S. Yoder, and H.S. Ald-winckle. 2009. Field evaluation o biological control o reblight in the eastern United States. Plant Disease 93:386-394.

University o Caliornia Statewide Integrated Pest Manage-ment Project. 1991. Integrated Pest Management or Apples

& Pears. University o Caliornia Division o Agriculture andNatural Resources. Publication 3340. Oakland, CA. p. 116.

Additional Resources

ElectronicUniversity o Caliornia Crop Inormation Asian Pear Indexhttp://ruitsandnuts.ucdavis.edu/crops/pear_asian.shtml

Horticultural inormation and links to actsheets on Asian

Pear production and disorders.

University o Caliornia website or European pearshttp://ruitsandnuts.ucdavis.edu/datastore/

Extensive links to sources o inormation on Europeanpear varieties, disorders, and economics.

Washington State University ree Fruit Research Center-Pear Entomologyhttp://entomology.trec.wsu.edu/pearent/

A new website designed or armers and eld workers thatprovides inormation and research on pear entomology.

Washington State University Cooperative ExtensionFireBlight: 7 Key Steps to Controlwww.ncw.wsu.edu/treeruit/reblight/control.htm

A direct, basic act sheet recommending seven key steps tore blight control.

Pennsylvania ree Fruit Production Guide: Asian Pearshttp://agsci.psu.edu/tpg

Discussion o Asian pears in general, and descriptions ocommon and less-common cultivars in the United States.

PrintJones, A. L. and H. S. Aldwinckle. 1990. Compendium o

Apple and Pear Diseases. APS Press, St. Paul, MN.Excellent descriptions and photos. $37 rom:

APS Press3340 Pilot Knob Rd.St. Paul, MN 55121-2097800-328-7560www.scisoc.org/

University o Caliornia Statewide Integrated Pest Manage-

ment Project. 1999. Integrated Pest Management or Applesand Pears (No. 3340). University o Caliornia, Oakland, CA.Available or $30 (plus $5 shipping), made payable to U.C.

Regents, rom:ANR Communication Services1301 S 46th StreetBuilding 478 MC 3580Richmond, CA 94804800-994-8849

Van der Zwet, om and Norman F. Childers (eds.) 1982.Te Pear. Horticultural Publications, Gainesville, FL.

Out o print, but obtainable through the Interlibrary LoanSystem at your local library.
http://www.fas.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pdfhttp://www.fas.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pdfhttp://www.fas.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pdfhttp://www.fas.usda.gov/htp/2011_Fruit.pdfhttp://www.fas.usda.gov/htp/2011_Fruit.pdfhttp://www.fas.usda.gov/htp/2011_Fruit.pdfhttp://www.agmrc.org/commodities__products/fruits/pears/http://www.agmrc.org/commodities__products/fruits/pears/http://www.agmrc.org/commodities__products/fruits/pears/http://www.extension.org/pages/62448/fire-blight-control-in-organic-pome-fruit-systems-under-the-proposed-non-antibiotic-standardhttp://www.extension.org/pages/62448/fire-blight-control-in-organic-pome-fruit-systems-under-the-proposed-non-antibiotic-standardhttp://www.extension.org/pages/62448/fire-blight-control-in-organic-pome-fruit-systems-under-the-proposed-non-antibiotic-standardhttp://www.ipm.ucdavis.edu/PMG/r603301111.htmlhttp://www.ipm.ucdavis.edu/PMG/r603301111.htmlhttp://www.ipm.ucdavis.edu/PMG/r603301111.htmlhttp://www.ipm.ucdavis.edu/PMG/r603301111.htmlhttp://www.extension.org/pages/62448/fire-blight-control-in-organic-pome-fruit-systems-under-the-proposed-non-antibiotic-standardhttp://www.extension.org/pages/62448/fire-blight-control-in-organic-pome-fruit-systems-under-the-proposed-non-antibiotic-standardhttp://www.agmrc.org/commodities__products/fruits/pears/http://www.agmrc.org/commodities__products/fruits/pears/http://www.fas.usda.gov/htp/2011_Fruit.pdfhttp://www.fas.usda.gov/htp/2011_Fruit.pdfhttp://www.fas.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pdfhttp://www.fas.usda.gov/htp/horticulture/Fresh%20Fruit/4-9-02%20US%20Pears.pdf


14/16


Appendix: Fire Blight, DiseaseResistance, and the DiseaseTriangleTe occurrence o diseaseany disease on any plant or ani-malis dependent on three actors: 1) a susceptible host;2) the presence o the disease-causing pathogen; and 3) asuitable environment or inection and disease development

(the disease triangle; see Figure 1). Tis act is very impor-tant to understanding re blight incidence in pear orchards,especially in terms o managing this potentially devastatingdisease in dierent parts o the country.

Figure 1. The Disease Triangle.

PresenceofPat

hogen

Susceptible Host

Suitable

Enviro

nment

for

Infection/D

isease

Development

Lets start at the top o the triangle with a corollary to point1: heritable disease resistance is rarely absolute. When a plant

breeder or plant pathologist reers to a pear cultivar as reblight resistant, he or she is speaking in relative terms. Usu-ally we read or hear something like somewhat resistant,very resistant, moderately resistant, or slightly suscepti-ble, o urther complicate matters, dierent researchers usedierent rating scales to describe resistance/susceptibilitythere is no agreed-upon standard. For example, some pub-lished studies rely on a 1 to 10 scale, which is usually basedon a visual estimate o damage, while others may use moreabsolute measurements, such as the centimeters o shoot tis-sue aected by re blight.

Regardless o the ailings o the various rating systems, thephenomenon o dierential resistance/susceptibility is realpear cultivars vary greatly in their reaction to the presenceoErwinia amylovora. Some cultivars, such as Magness andShinko, will only rarely suer any re blight strikes, and, ithey do, the blight will rarely intrude into any wood older than

one year. In contrast, when all three actors o the disease tri-

angle conspire, re blight can sometimes kill even mature trees

o susceptible European cultivars in a single year.

Te second ace o the trianglepresence o the pathogen

is the one that seems to prompt most o our eorts as grow-

ers. When we spray copper, Blight Ban, or one o the antibi-

otics, we are trying to reduce or exclude (in the case o Blight

Ban) the pathogen rom potential inection sites. Tere is alsoa geographic component to this part o the triangle, as E.

amylovorais much less prevalent in some parts o the world

than in others.

Te third ace o the trianglean environment conducive to

the diseaseis also related to geography, mostly by climate.

Where the climate is warm and wet, especially in the spring,

re blight inection and development are avored. Te more

arid parts o the western United States are not nearly as prone

to re blight problems as most o the East. But these large cli-

matic and geographic eatures are not the only components oa disease-promoting or disease-suppressive environmentthe

orchardist can manipulate parts o the orchard micro-envi-

ronment to help suppress disease development. For example,

reducing ertilization can limit ast-growing succulent tissue,

which is especially prone to inection and seems to provide

the disease its astest entry into the wood.

Another practice that can be adjusted to alter the orchard

environment is pruning, which can open up a tree to allow

more-rapid drying o plant tissues and thus prevent dis-

ease. However, a grower in a dierent situation might need

to reduce pruning in order to avoid ostering the lush shoot

growth (which is more susceptible to re blight) that usually

ollows heavy pruning.

Tere is considerable interplay, o course, between the aces o

the disease triangle. It is especially important to understand

that given high levels o inoculum and the proper environ-

mental conditions, medium levels o varietal resistance can be

overcome. For example, Shin-Lireleased by the University

o Caliornia as re blight resistantis relatively resistant

in the climate o Caliornia, but can suer severe re blight

inection in the Southeast i not adequately protected by

spraying. I you plant Bartlett in South Carolina, or another

example, and dont spray, you can watch the disease triangle

imitate the Bermuda riangle, as your trees disappear one by

one and year by year.


15/16


Notes


16/16

Page 16 ATTRA

Organic Pear Production

By Guy K. Ames and Holly Born

NCAT Agriculture Specialists

Published 2003

Revised May 2012 by Guy K. Ames

NCAT Agriculture Specialist

NCAT

Tracy Mumma, Editor

Kayla Lester, Production

This publication is available on the Web at:

www.attra.ncat.org

IP167

Slot 36

Version 051612

Organic Pears

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