O P P RGANIC EAR RODUCTION HORTICULTURE PRODUCTION GUIDE Abstract : This introduction to commercial organic pear production covers pear diseases, disease-resistant cultivars, insect and mite pests and their treatment, Asian pears, and marketing. Electronic and print resources are provided for further research. By Martin Guerena and Holly Born ticles, and websites (see NCAT Agriculture Specialists the Further Resources Updated by Tracy Mumma section at the end of this April 2003 document). For cultural information more spe- Introduction cific to organic produc- tion (organic fertiliza- 'WWW.clipart.com 2003 In most of the U.S., pears may be the easiest of tion, organic weed control, etc.) request the tree fruits to produce organically or with ATTRA(cid:146)s Overview of Organic Fruit Production. minimal spraying. Pears(cid:146) fertility requirements are not high, they are adapted to a wide range of Pears have most of the same pest and disease climates and soils, and they have fewer pest problems that apples have, but usually to a con- problems than other tree fruits. siderably lesser degree. ATTRA(cid:146)s Organic and Low-Spray Apple Production identifies pests and Standard cultural considerations(cid:151)such as prun- suggests organic remedies that are just as ap- ing, choice of rootstock, planting, spacing, and propriate to pears; therefore, most of these prob- thinning(cid:151)are generally the same for organic and lems will not be discussed further in this publi- conventional growers. For this type of cultural cation. However, because of its importance and information consult your county or state Coop- prevalence on pears, fireblight will be consid- erative Extension Service and/or find the infor- ered in more depth. Other pests and diseases mation in any number of orcharding texts, ar- peculiar or especially troublesome to pears will also be discussed. Related ATTRA Publications (cid:149) Overview of Organic Fruit Production Table of Contents (cid:149) Postharvest Handling of Fruits & Veg- Introduction........................................... 1 etables Diseases .................................................. 2 (cid:149) Insect IPM in Apples: Kaolin Clay Insect and Mite Pests............................ 5 (cid:149) Farmscaping to Enhance Biological Con- Asian Pears............................................. 6 trol Economics and Marketing .................. 7 (cid:149) Biointensive Integrated Pest Management References.............................................. 8 (IPM) Additional Resources........................... 9 (cid:149) Organic & Low-spray Apple Production Appendix: Fireblight, Disease (cid:149) Organic Grape Production (cid:149) Organic / Low Spray Peach Production Resistance, and the Disease (cid:149) Low Spray & Organic Plum Production Triangle................................................... 9 ATTRA is the national sustainable agriculture information service, operated by the National Center for Appropriate Technology through a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California. Comparing a Pair of Pears European pears Asian pears Scientific names Pyrus communis Pyrus ussuriensis P. serotina P. bretschneideri Common cultivars Bartlett, Bosc, D(cid:146)Anjou, Seckel, 20th Century, Shinseiki, Magness, Maxine, Moonglow, Korean Giant, Shinko, Comice Chojuro, Niitaka Texture and flavor Buttery smooth and sweet. Crisp. Flavors vary widely, including bland, sweet, sweet-tart, pineapple-like, and more. Color Green to yellow, though Green, yellow to golden, russetted types are dull bronze, russetted bronze, and and there are a few red types. many types with white lenticels (spots). Shape Pyriform (i.e., round & bulb- Most cultivars are round. like on the calyx end, Some are misshapenly narrowing to a slender neck at round. A few are stem end). somewhat pyriform. Harvest and postharvest Harvest before fully ripe. Allow to tree-ripen. Ready Allow to ripen (cure) at room to consume or sell. temp. Buyer usually does curing. Pests and diseases Same as for Asian (see text). Same as for European (see text). Diseases wither and turn black or brownish black, as if Fireblight scorched. Most branch tips, once infected, wilt rapidly, taking on the characteristic shape of a Fireblight, caused by the bacterium Erwinia (cid:147)shepherd(cid:146)s crook.(cid:148) The bacteria gain entry to amylovora, is one of the most serious and eco- the tree through blossoms or lush new growth nomically damaging diseases of pears. Occur- and, once inside, begin to work toward the roots. ring throughout the pear(cid:146)s range, it is particu- If the disease spreads unchecked to the trunk and larly troublesome in the humid eastern United roots, it can kill the tree; however, in resistant States. Infection is triggered by heat and mois- varieties the bacteria rarely invade beyond young ture, and can spread rapidly(cid:151)even within a wood. Under the bark, the bacteria form a can- matter of hours. It can be transmitted by bees, ker where they will survive the winter, only to aphids, psylla, or other insects, and can also be infect more trees the next year. If on a warm day spread by blowing wind and rain. Pruning can you see pustules on a tree, oozing an orange- be another source of infection. Affected branches brown liquid, you are looking at fireblight (1). PAGE 2 //ORGANIC PEAR PRODUCTION Fireblight development is greatly favored by the general it is less effective. Both streptomycin and presence of young, succulent tissues. Cultural terramycin are listed as approved substances for practices that favor moderate growth of trees are fireblight control in the National Standards on recommended. These include using only half as Organic Agricultural Production and Handling much compost as for apples, never using manure, (5). and avoiding heavy populations of clovers and other legumes around the base of the tree (2). Bordeaux mix (copper sulfate and lime) and other Pruning should also be limited, and only mini- copper formulations sprayed at green-tip stage mum fertilization applied. are organic options that provide some protection from fireblight infection. For best results, these Choosing fireblight-resistant pear cultivars is a formulations should be applied to all the trees in good start to managing fireblight, but it is by no a block, not only the blight-susceptible cultivars means a panacea (see the Appendix (cid:147)Fireblight, (6). Copper treatments can cause fruit scarring, Disease Resistance, and the Disease Triangle(cid:148)). and are phytotoxic to some cultivars, so careful There are several European-type pears with a application is important. comparatively high level of fireblight resistance (Ayres, Magness, Potomac, Warren, Maxine, In 1996 a biocontrol product called BlightBanfi Moon Glow, Tyson, Honeysweet, Kieffer, etc.) A506 came on the market, labeled primarily for that are adapted to most of the contiguous United reducing frost damage, but also for fireblight States. Clapps, Bartlett, Comice, Anjou, Bosc, and suppression. BlightBan is a formulation of the most other cultivars that are not expressly de- bacterium Pseudomonas fluorescens, strain A506. scribed as (cid:147)fireblight resistant(cid:148) in a nursery cata- P. fluorescens is a non-pathogenic competitor with log should be considered susceptible. E. amylovora, and as such does not directly kill propagules of E. amylovora; rather, it occupies the Asian-pear cultivars also vary in their resistance same sites that E. amylovora would, provided it to fireblight. Shinko has a high level of resis- gets there first. Therefore, in order to be effec- tance, while Ya Li, Chojuro, Shinsei, and Seuri tive, BlightBan should be applied to newly-open- are among the moderately resistant varieties (3). ing flowers (multiple applications will probably Shinseiki has been rated as (cid:147)resistant(cid:148) by Ken- be necessary) or applied in combination with tucky researchers and (cid:147)susceptible(cid:148) by Alabama streptomycin (P. fluorescens strain A506 is resis- A&M researchers. Korean Giant and Shin Li are tant to streptomycin). In fact, research indicates listed as resistant in some literature, but grower that fire blight suppression is best when strepto- experience with heavy fireblight pressure in Ar- mycin and BlightBan are combined. kansas indicates that they are at best only slightly resistant (4). Blight resistance for some cultivars Using these two substances together can reduce appears to vary with growing conditions. It may the amount of streptomycin sprayed each year, be some time before all Asian pear cultivars, be- which may help to protect the antibiotic(cid:146)s effec- ing relatively new in the U.S., are well classified tiveness. By itself, BlightBan can provide up to in terms of blight resistance. 50% suppression, but not control. It cannot be used in combination with copper sprays. The Preventing infection is the next key to fireblight biocontrol bacteria live only about three weeks control. Sprays of agricultural-grade streptomy- in the orchard, and there is no carry-over from cin, applied at early bloom to prevent infection, year to year. BlightBan is marketed by J. R. have been the standard commercial control since Simplot Company/Plant Health Technologies the 1950s. In some regions, particularly Western (7). Note that it is not registered for use in all apple-growing areas, E. amylovora has developed states. resistance to streptomycin. In order to preserve the effectiveness of this antibiotic, it is important A computer software program called Maryblyt(cid:153) not to spray it excessively. In areas where resis- is available to help in timing antibiotic sprays for tance has already developed, terramycin (Myco- their most efficient application against fireblight. Shieldfi) can be used as a substitute, though in The grower enters daily minimum and maxi- //ORGANIC PEAR PRODUCTION PAGE 3 mum temperatures, rainfall, and stage of blos- vars in particular. Because the presence of blos- som development, and the program predicts in- som-blast bacteria allows ice crystals to form at fection events and symptom development for higher-than-normal temperatures, the disease most phases of fireblight. Further information increases the incidence of freeze damage during on the program is available at the USDA(cid:146)s cold wet weather. Asian pears are especially af- Kearneysville, West Virginia, web site <http:// fected because their early bloom makes them afrsweb.usda.gov/fireblight/fb8.htm>. In the more susceptible to frost injury (8). Of the Asian- Pacific Northwest the similar but freely-distrib- pear cultivars mentioned above, Shinko and Ya uted Cougarblite Model <http:// Li are moderately resistant to P. syringae. www.ncw.wsu.edu/models.htm> is more often used to help time spraying, and elsewhere other Controlling this disease is difficult because its degree-hour models from local sources may be occurrence is widespread on many plant species more appropriate. and not easily predicted; once symptoms appear, control efforts are too late. Protecting orchards Once fireblight infection has occurred, there is from frost damage can limit injury. An early no spray or other treatment, beyond quickly cut- application of BlightBanfi A506 can help reduce ting out newly infected limbs, that will minimize frost damage potential by excluding the ice- damage. However, infection has almost certainly nucleating bacteria. In California, the applica- extended beyond what the grower sees; there- tion of fixed copper at the green-tip stage fol- fore, it is all too easy to spread the disease by lowed by streptomycin at early bloom has pro- trying to prune it out during the growing sea- vided reasonable control. This treatment has also son. If you do cut during the growing season, been used in Oregon, where cool wet weather remove all blighted twigs, branches, and cankers makes blossom blast a particular problem in pear at least 8 inches(cid:151)some sources recommend 12(cid:151) production. Streptomycin or terramycin applied below the last point of visible infection, and burn at early bloom to control fire blight also help to them. After each cut, the shears can be sterilized control blossom blast, although the most effec- in a strong bleach or Lysolfi solution (1 part tive timing of application for the two diseases is household bleach or Lysol to 4 parts water) to somewhat different. help avoid transmitting the disease from one branch to another, although there is some dis- Pear scab agreement about the effectiveness of disinfection. Lysol is less corrosive than bleach to the metal Pear scab (Venturia pirina), a fungal disease parts of the pruners. Some have found it more closely related to apple scab, is neither as com- convenient to use a spray can of Lysol disinfec- mon nor as economically important on pears as tant carried in an apron rather than a plastic hol- apple scab is on apples. Nevertheless, it can cause ster or glass jar with a liquid solution. economic damage by marring the appearance of the fruit. Pear scab causes lesions on leaves, During the winter, when the temperature ren- shoots, and fruit, and(cid:151)unlike apple scab(cid:151)in- ders the bacteria inactive, pruning out fireblight- fects twigs, where it can overwinter. Pear culti- infected wood can proceed without sterilization vars differ in their susceptibility to scab. Organic of pruning tools, and need not extend as far be- control is identical to that for apple scab (9), usu- low the visible canker. ally consisting of treatment with sulfur, lime-sul- fur, or Bordeaux mixture. See ATTRA(cid:146)s Organic Blossom blast and Low-spray Apple Production for details, includ- ing the use of the Mills Table to predict infection Another bacterial disease, blossom blast (causal periods. organism: Pseudomonas syringae, not to be con- fused with Psedomonas fluorescens discussed Other diseases above), may afflict pears, usually as a blossom blight resulting in reduced fruit set. It can also Two foliar diseases, fabraea leaf spot (Fabraea cause twig dieback and bark cankers, and may maculata) and mycosphaerella leaf spot lead to severe wood damage of Asian-pear culti- (Mycosphaerella pyri), are usually no problem in PAGE 4 //ORGANIC PEAR PRODUCTION sprayed orchards but can reach damaging levels control has made organic pear production viable in unsprayed ones (9). Susceptible cultivars, for the first time in states like Michigan (10). The which include nearly all European pears, can be psylla also has a number of natural enemies such defoliated, resulting in reduced buds and as predatory flies, minute pirate bugs, and lacew- dwarfed or(cid:151)if the fruit itself is infected(cid:151)unmar- ing larvae. In organic orchards parasites and ketable fruit. Sprays for pear scab, such as Bor- predators can help control psylla below economi- deaux mixture, will generally control these two cally damaging levels, especially when combined maladies as well. Also, Surround(cid:153), a kaolin- with a program of oil treatments (11). clay-based insect repellant, is registered and la- beled for suppression of fabraea leaf spot. More True bugs information on Surround is available in ATTRA(cid:146)s Insect IPM in Apples: Kaolin Clay. Stink bugs, tarnished plant bug, and other true bugs (insects in the order Hemiptera) will readily Insect and Mite Pests feed on pears throughout the growing season. Early feeding damage may result in a pucker or Many of the same pests that affect apples also dimple in the fruit. Mid- and late-season feed- prey on pears, although often to a lesser degree. ing often results in the development of so-called More information on dealing with these pests can (cid:147)stone cells(cid:148) immediately beneath the feeding be found in ATTRA(cid:146)s Organic and Low-Spray site. These stone cells are very hard and can se- Apple Production. Some of the pests that particu- riously compromise the marketability of affected larly affect pears are discussed below. Proper fruit. pest identification and orchard scouting are key to implementing successful IPM programs. Some fruit and nut growers reduce true-bug ATTRA(cid:146)s Biointensive Integrated Pest Management damage by maintaining unmown leguminous (IPM) publication provides additional informa- trap crops (clovers, vetches, peas, etc.) near the tion. orchard (12). Unmown areas and cover crops can also serve as habitat for predator insects(cid:151) Pear psylla for more information, see the ATTRA publica- tion Farmscaping to Enhance Biological Control. The pear psylla (Cacopsylla pyricola), an aphid- Surround(cid:153) is labeled for suppression of stink- like insect whose only host is the pear, is the bugs and lygus bugs in pears. Also, some of the crop(cid:146)s most significant insect pest. In conjunc- relatively new biological insecticides derived tion with fireblight, pear psylla is largely respon- from the seeds of the neem tree are effective sible for the decline in Eastern pear production. against true bugs on fruit crops. For example, The honeydew left by the psylla damages the Aza-Direct(cid:153), which is listed by the Organic fruit by supporting growth of sooty mold and Materials Review Institute (OMRI) for use in or- causing a black russeting; these two effects ac- ganic production, is labeled for use on all pome count for most of the economic damage caused fruits for the control of weevils, thrips, true bugs, by the psylla. It is also an important vector of leafhoppers, aphids, leafrollers, cutworms, flies, fireblight and (cid:147)pear decline disease,(cid:148) and can and mites. Aza-Direct is produced by Gowan weaken trees in areas of heavy infection. Company (13). Although the psylla develops resistance to insec- Mites ticides, it can usually be controlled either with dormant oil sprays or with sulfur sprays (but not In high enough numbers, pearleaf blister mites a combination of the two, which damages plants.) (Phytoptus pyri) and pear rust mites (Epitrimerus Insecticidal soap can reduce active populations pyri) can reduce the photosynthetic efficiency of during the growing season. Fortunately, the re- leaves and cause russeting on fruit. Both species cently-introduced Surround(cid:153) (discussed above will likely be more troublesome in dusty condi- under Other diseases) is effective against pear tions, as the dust interferes with their natural psylla. In fact, use of Surround for pear psylla predators. These predators(cid:151)including green //ORGANIC PEAR PRODUCTION PAGE 5 lacewings, predatory mites, and various species Peshastin Creek Growers Areawide of ladybird beetles, as well as bigeyed bugs, Organic Project minute pirate bugs, and predatory thrips(cid:151)will In a Washington valley, twelve family-owned usually control mite outbreaks if they are not dis- orchards with approximately 300 acres of rupted by dust or pesticides. Orchard monitor- pears have joined together to establish ing can help establish whether adequate num- an areawide insect pest management bers of beneficial insects are present. If not, hor- program based on the use of organic insect- ticultural oils sprayed during the dormant sea- control tactics. son can suppress mite eggs through suffocation. Dennis Nicholson and Rich Miller Neither horticultural oils nor other materials Co-Chairpersons approved for organic production provide eco- P.O. Box 55 nomic control of damaging populations. Peshastin, WA 98847 (509)548-4207 Another pest that contributes to poor yields and [email protected] smaller fruit is the spider mite. Dormant horti- http://entomology.tfrec.wsu.edu/ cultural oils and insecticidal soaps can both help pearent/pcg%20home%20page.htm control spider mite outbreaks. Neem-based bio- logical insecticides are also labeled for control- shape, color, and taste. Only about a dozen vari- ling mites on pears. European-pear cultivars are eties are commonly grown in U.S. commercial more sensitive to mite feeding than Asian pears, orchards. and any pear that is drought-stressed will be more susceptible to mite damage (14). Asian pears are slightly less cold-hardy than Eu- ropean types; they may suffer tissue damage at Other insects temperatures below (cid:150)10(cid:176) F but are generally hardy to (cid:150)20(cid:176), making them best adapted to Other insect pests that may affect pears include USDA climatic zones 5(cid:150)9. Most Asian pears codling moth, apple maggot, scale, and plum bloom slightly earlier than their European coun- curculio. These insects are covered in ATTRA(cid:146)s terparts and may lose some blooms or buds to Organic and Low-spray Apple Production publica- freezing in areas with a highly variable spring tion. The pear slug (actually a sawfly larva) climate. causes leaf damage; it can be controlled with a forceful stream of water, soap, or wood ashes. Culture of Asian pears is similar to that of Euro- The leafroller complex(cid:151)including tufted apple pean types, but not identical. One significant bud moth, variegated leafroller, and redbanded difference is the common tendency for many of leafrollers(cid:151)represents another potential, but the Asian types to set too heavy a fruit crop, comparatively minor, pear pest problem. Mat- which requires hand thinning of young fruit soon ing disruption tools that are effective for some after bloom. Shinko, a popular cultivar because leafrollers are being developed. In addition, there of its high fruit quality and fireblight resistance, are biological insecticides labeled for control of is especially prone to this problem. If not prop- leafhoppers, aphids, and leafrollers, among other erly thinned, Shinko and any other heavy-bear- pests. ing Asian pear cultivar will not be able to prop- erly mature such a load. Fruit size and quality Asian Pears will suffer. On the other hand, thinning to pro- mote fruit size may result in reduced yield per Because they are relatively new to much of the acre compared to European pear varieties. United States, Asian pears deserve some addi- tional comment. A crisp, juicy fruit, Asian pears Another difference between Asian and European are also known as Oriental pears, nashi, sand pears is that Asian pears ripen on the tree(cid:151)they pears, apple pears, or salad pears. The more than do not have to be picked and then cured like 1,000 varieties of Asian pear range widely in European pears. This is an advantage for most PAGE 6 //ORGANIC PEAR PRODUCTION growers, especially growers who are retailing based on these factors, and the premium that direct to consumers. The fruit can be tree rip- organic growers can expect to receive for their ened and is ready to eat when picked, or can be product is unpredictable at best. held in cold storage. You do not have to educate the buyer about curing, as you might with Euro- The market for pears is weaker than it could be, pean pears. largely because of consumers(cid:146) unfamiliarity with the different types of pears and how to use them. One survey showed that Bartletts and winter It is important to note that the delicate fruit of pears were consumed by no more than half of many Asian-pear varieties must be carefully America(cid:146)s households, and then only occasion- handled during and after harvest to minimize ally. A market study funded by the Pear Bureau bruising, punctures, and roller marks. The skin showed that only 3 out of 10 people have tried of Asian pears discolors quickly following rough d(cid:146)Anjou pears, and 2 out of 10 have tried Boscs. handling, making careful picking and packag- One of the obstacles limiting pear consumption ing a necessity, and mechanical handling risky. is that many consumers do not know how to To prevent damage to Asian pears, it may be best ripen them. Providing information on ripening to pack them into padded boxes or trays in the may help increase sales (though the Pear Bureau field where they are picked. study also found that most people preferred to buy pears already ripened). A substantial per- More information on Asian pears can be found centage of purchases are impulse buys, so ap- in the sources provided in the References and pearance is critical. Many appearance problems Further Resources sections. come from fruit being handled by retail employ- ees and consumers. Pears should be handled Economics and Marketing gently, no matter what stage of ripeness they have reached. Rough handling causes brown Worldwide, China is by far the world(cid:146)s largest marks on the skin that may not appear until the pear-producing country, followed by Italy. The fruit has begun to ripen, and will decrease cus- United States is the third-largest pear producer tomer appeal. Sources of consumer, food-service, in the world. Export markets are important for and other trade-education materials related to U.S. producers(cid:151)more than 30% of the U.S. fresh European pears are available from the Pear Bu- pear crop is shipped to foreign markets (15). At reau Northwest (17). one time pears were grown commercially on a large scale throughout the United States. How- The market for Asian pears is mixed. Until 1995 ever, because of the prevalence of fireblight in or so, the wholesale market for Asian pears was the humid eastern and southern states, most pear quite open and prices were high, particularly on production has been relocated to the drier areas the West Coast and in cities with large Asian- of the Pacific Northwest. More than 95% of the American populations. But Asian pears have pears produced in the U.S. are grown in Wash- been heavily planted in California for more than ington, Oregon, and Northern California (16). 20 years, and those orchards are now mature and Bartletts remain the most popular pear variety bearing, more than meeting local demand and grown commercially in the U.S., outnumbering causing price drops in some areas. all other species combined. On the other hand, outside of California, Asian Bartlett pear production has been declining pear growers that serve a retail clientele(cid:151)espe- slightly since 2000, resulting in higher prices for cially a local Asian-American population(cid:151)report producers who continue to grow them (15). In brisk sales and good prices from locations across general, pear prices tend to fluctuate based on the country (3, 4). Offering taste sampling of fruit, crop size(cid:151)which can be highly variable on ac- where practical and allowed by local health regu- count of weather and fruit set rates(cid:151)and on the lations, is probably a good idea for building mar- number of growers producing pears in a given kets, since so many Americans are still unfamil- year. Fluctuation in the organic market is also iar with Asian pears. //ORGANIC PEAR PRODUCTION PAGE 7 Asian pears are breaking out of their niche to join 10) Elkins, R.B., R. A. Van Steenwyk, L. G. the mainstream market, and may represent an Varela, and C. Pickel. 2001. UC opportunity for producers as market awareness IPM Pest Management Guidelines: Pear and demand continue to grow. Psylla. UC DANR Publication 3339. Accessed August 2002. <http:// References www.ipm.ucdavis.edu/PMG/ r603301111.html>. 1) Agrios, G. 1978. Plant Pathology. Aca- 11) Anon. 2002. Organic pears are a viable demic Press, New York, NY. p. 457(cid:150)463. opportunity for Michigan growers. IPM Report. Spring. p. 1. Accessed August 2) Hall-Beyer, Bart, and Jean Richard. 1983. 2002 at <http://www.msue.msu.edu/ Ecological Fruit Production in the North. ipm/ipmrptv8n1.htm>. Jean Richard Publishing Co., Trois-Rivieres, Quebec, Canada. p. 33(cid:150)34. 12) Anon. 1999. Pea patch diverts stinkbugs. Common Ground. Autumn. p. 4. 3) Jones, Terry, and Ed Fackler. 1995. Asian pears(cid:151)A past & future in Kentucky. 13) Gowan Company Pomona. Fall. p. 31(cid:150)35. P.O. Box 5569 Yuma, AZ 85366-5569 4) Ames, Guy. 2000. Personal communica- 800- 883-1844 ext. 2 tion. http://www.aza-direct.com/ 5) Anon. 2000. The National List of Allowed 14) University of California Statewide and Prohibited Substances Description of Integrated Pest Management Project. Regulations General Requirements. Ac- 1991. Integrated Pest Management for cessed August 2002. <http:// Apples & Pears. University of California www.ams.usda.gov/nop/NationalList/ Division of Agriculture and Natural FinalRule.html>. Resources. Publication 3340. Oakland, CA. p. 116. 6) Steiner, Paul W. 1995. Maryblyt beats fire blight. American Fruit Grower. 15) Perez, Agnes. 2001. Smaller 2001 U.S. Pear February. p. 30(cid:150)31. Crop to Boost Prices. Agricultural Outlook. November 2001. p.4. 7) Plant Health Technologies POB 15057 16) Foreign Agricultural Service. 1999. World Boise, ID 83715 Pear Situation. FAS Online. Accessed July 800-535-9101 2002. <http://www.fas.usda.gov/htp2/ circular/1999/99-04/pear.htm>. 8) Elkins, R.B., and W. D. Gubler. 2001. Plant Pathology, UC IPM Pest Man- 17) Pear Bureau Northwest agement Guidelines: Pear. UC DANR 4382 SE International Way Ste. A Publication 3339. Accessed August 2002. Milwaukie, OR 97222-4635 <http://www.ipm.ucdavis.edu/PMG/ 503- 652-9720 r603100111.html>. http://www.usapears.com/ 9) Jones, Alan, and Turner B. Sutton. 1996. Diseases of Tree Fruits in the East. NCR 45. Michigan State University, East Lansing, MI. p. 22(cid:150)23. PAGE 8 //ORGANIC PEAR PRODUCTION Additional Resources (electronic): Pears (No. 3340). University of California, Oak- land. 216 p. University of California Crop Information Asian Available for $30 (plus $5 shipping), made Pear Index payable to U.C. Regents, from: http://fruitsandnuts.ucdavis.edu/crops/ University of California pear_asian.shtml Division of Agriculture & Natural Horticultural information and links to factsheets Resources on Asian Pear production and disorders. Communication Services-Publications 6701 San Pablo Ave. University of California website for European Oakland, CA 94608 pears 1-800-994-8849 http://fruitsandnuts.ucdavis.edu/crops/ pear.shtml Van der Zwet, Tom and Norman F. Childers Extensive links to sources of information on Eur- (eds.) 1982. The Pear. Horticultural Publica- opean pear varieties, disorders, and economics. tions, Gainesville, FL. 503 p. Out of print, but obtainable through the Inter- Washington State University Tree Fruit Research library Loan System at your local library. Center(cid:151)Pear Entomology http://entomology.tfrec.wsu.edu/pearent/ A new website designed for farmers and field workers, and devoted to information and current Appendix: Fireblight, Disease Resistance, research on pear entomology. and the Disease Triangle Washington State University Cooperative Exten- sion(cid:151)Fire Blight: 7 Key Steps to Control Susceptible Host http://www.ncw.wsu.edu/fbcontrol.htm nte A direct, basic fact sheet recommending 7 key meeas steps to fireblight control. onDis PPhteetnaprn:s/sD yR/iltesvfccpauongsmi.sacimao Tnser. penoefsd uAFe.rdseui dacintuu P /lptrpeiovaadrarsurt 1sicn/ti pgoenanr Gte1rua5ilbd, .aehn:t Adm sdiea-n Presence ofPathogen Suitable Envirfor Infection/Development scriptions of common cultivars in the United Fig. 1: The Disease Triangle States, and less-common cultivars. Additional Resources (print): The occurrence of disease(cid:151)any disease on any plant or animal(cid:151)is dependent on three factors: Jones, A. L. and H. S. Aldwinckle. 1990. Com- 1) a susceptible host, 2) the presence of the dis- pendium of Apple and Pear Diseases. APS Press, ease-causing pathogen, and 3) a suitable envi- St. Paul, MN. 100 p. ronment for infection and disease development Excellent descriptions and photos. $37 from: (the (cid:147)disease triangle;(cid:148) see Figure 1). This fact is APS Press very important to understanding fireblight inci- 3340 Pilot Knob Rd. dence in pear orchards, especially in terms of St. Paul, MN 55121-2097 managing this potentially devastating disease in 1-800-328-7560 different parts of the country. http://www.scisoc.org/ Let(cid:146)s start at the top of the triangle with a corol- University of California Statewide Integrated lary to point 1: heritable disease resistance is Pest Management Project. 1999 (2nd Edition). rarely absolute. When a plant breeder or plant Integrated Pest Management for Apples and pathologist refers to a pear cultivar as (cid:147)fireblight //ORGANIC PEAR PRODUCTION PAGE 9 resistant,(cid:148) he or she is speaking in relative terms. which is especially prone to infection and seems Usually we read or hear something like (cid:147)some- to provide the disease its fastest entry into the what resistant,(cid:148) (cid:147)very resistant,(cid:148) (cid:147)moderately re- wood. sistant,(cid:148) (cid:147)slightly susceptible,(cid:148) etc. To further complicate matters, different researchers use dif- Another practice that can be adjusted to alter the ferent rating scales to describe resistance/suscep- orchard environment is pruning, which can tibility(cid:151)there is no agreed-upon standard. For (cid:147)open up(cid:148) a tree to allow more rapid drying of example, some published studies rely on a (cid:147)1 to plant tissues and thus prevent disease. However, 10(cid:148) scale, which is usually based on a visual esti- a grower in a different situation might need to mate of damage, while others may use more ab- reduce pruning in order to avoid fostering the lush solute measurements, such as the centimeters of shoot growth (which is more susceptible to shoot tissue affected by fireblight. fireblight) that usually follows heavy pruning. Regardless of the failings of the various rating There is considerable interplay, of course, be- systems, the phenomenon of differential resis- tween the faces of the disease triangle. It is espe- tance/susceptibility is real(cid:151)pear cultivars vary cially important to understand that given high greatly in their reaction to the presence of Erwinia levels of inoculum and the proper environmen- amylovora. Some cultivars, such as Magness and tal conditions, medium levels of varietal resis- Shinko, will only rarely suffer any fireblight tance can be overcome. For example, Shin-Li(cid:151) strikes, and, if they do, the blight will rarely in- released by the University of California as trude into any wood older than one year. In con- (cid:147)fireblight resistant(cid:148)(cid:151)is relatively resistant in trast, when all three factors of the disease triangle the climate of California, but can suffer severe conspire, fireblight can kill even some older trees fireblight infection in the Southeast if not ad- of susceptible European cultivars in a single year. equately protected by spraying. If you plant Bartlett in South Carolina, for another example, The second face of the triangle, presence of the and don(cid:146)t spray, you can watch the disease tri- pathogen, is the one that seems to prompt most angle imitate the Bermuda Triangle, as your trees of our efforts as growers. When we spray cop- disappear one-by-one and year-by-year. per, Blight Ban(cid:153), or one of the antibiotics, we are trying to reduce or exclude (in the case of Blight Ban) the pathogen from potential infec- By Martin Guerena and Holly Born tion sites. There is also a geographic component NCAT Agriculture Specialists to this part of the triangle, as E. amylovora is much Updated by Tracy Mumma less prevalent in some parts of the world than in others. Edited by Richard Earles Formatted by Cynthia Arnold The third face of the triangle(cid:151)an environment conducive to the disease(cid:151)is also related to ge- April 2003 ography, mostly by climate. Where the climate is warm and wet, expecially in the spring, fireblight infection and development are favored. The more arid parts of the western U.S. are not nearly as prone to fireblight problems as most of The electronic version of Organic Pear Production is located at: the East. But these large climatic and geographic HTML features are not the only components of a dis- http://www.attra.ncat.org/attra-pub/pear.html ease-promoting or disease-suppressive environ- PDF ment(cid:151)the orchardist can manipulate parts of the http://www.attra.ncat.org/attra-pub/PDF/pear.pdf orchard micro-environment to help suppress dis- ease development. For example, reducing fer- IP167 tilization can limit fast-growing succulent tissue, PAGE 10 //ORGANIC PEAR PRODUCTION