Potatoes: Organic Production and Marketing


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Potatoes: Organic Production and Marketing

  1. 1. Potatoes: Organic Production and Marketing A Publication of ATTRA—National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.orgBy Rex Dufour, This publication outlines approaches to organic and sustainable potato production. PracticesTammy Hinman and include fertility and nutrient management; organic and biorational pest management for insects,Jeff Schahczenski diseases and weeds; and storage and marketing.NCAT AgricultureSpecialists Introduction organic potato sales appear to be strong,© 2009 NCAT This publication outlines many of the it can be difficult to enter wholesale mar- practices used in organic and sustainable kets due to storage complications and potato production. While organic potato market control. These factors are Table of Contents production can yield a premium price discussed in greater detail as well.Section I: for your product, the production consid- Because each farm is a unique combi-Organic production erations are significant. This publication nation of soil, climate, environment,overview ...................................1 discusses organic soil and pest manage- management and marketing techniques,Fertility and nutrientmanagement ..........................3 ment strategies that help ensure growth it is important to plan and assess which Organic matter ...................4 of healthy and vigorous plants. Strategies practices described here are appropriate Rotations ...............................4 include choosing potato varieties suitable for a particular farm. There are numerousSection II ..................................9 for the area and intended use; using dis- potato production manuals that are spe-Weed management .............9 ease-free seed potato sources; appropri- cific to regions within the United States.Nematode management ...9 ate soil fertility and management; weed, For further information on region-specificDisease management ...... 10 disease and insect control; harvesting and potato production in general, withinInsect management...........14 methods and crop storage. your region, consult your local Coopera-Section III ............................. 21 Economic and market evaluation are tive Extension Service or call the ATTRAHarvesting ............................ 21 equally important topics in organic information line at 1-800-346-9140 forStorage................................... 23Economics and marketing potato production. While direct-marketed county extension office contacts.of organic potato Section Iproduction ........................... 23 Profile of organic potato grower: Gene Thiel ......... 26 Profile of organic potato grower: Mike Heath........ 30 Organic production overview analyses and nutrient crediting help pro- ducers avoid excess fertilizer applications.References .............................31 Organic farmers adhere to certificationFurther resources ............... 33 Sustainable farming methods also include guidelines that exclude the use of syn- thetic fertilizers and pesticides. Producers using these techniques are able to market their products as organic if they have gone through a certification process. If you are interested in becoming certified organic,ATTRA—National Sustainable ATTRA has many publications that canAgriculture Information Service(www.ncat.attra.org) is managed help you through the transition process.by the National Center for Appro- The ATTRA publication Guide to ATTRA’spriate Technology (NCAT) and isfunded under a grant from the Organic Publications will help you get offUnited States Department of to the right start.Agriculture’s Rural Business-Cooperative Service. Visit theNCAT Web site (www.ncat.org/ Organic production practices maximizesarc_current.php) for the use and recycling of on-farm nutri-more information onour sustainable agri- ent sources, including animal and green Potato plant. Photo by Dianne Earl. Courtesy of theculture projects. manures. Techniques such as accurate soil National Education Network.
  2. 2. soil-building and -conserving practices interested in transitioning to organic such as adding organic matter and potato production. minimum-tillage approaches. Biointensive The National Organic Program certi- integrated pest management is also a sus- fication standards require producers tainable farming method. to grow potatoes from organically certified The primary goal of biointensive IPM seed potatoes. The limited availability is to provide guidelines and options for of organic potato seed stock may limit the effective management of pests and the selection of specific varieties and beneficial organisms in an ecological context. larger quantities. The flexibility and environmental compati-Related ATTRA bility of a biointensive IPM strategy makes itPublications Zuseful in all types of cropping systems. Organic seed potato stock must be sourcedSustainable Soil See the ATTRA publication Biointensive for certified organic production unlessManagement Integrated Pest Management for more infor- organic seed stock is not available in the same quality, quantity or form as nonorganicBiointensive mation on this subject. stock. Examples of the quality, quantity andIntegrated PestManagement Two important factors that contribute to form clauses are: developing a sustainable and profitable farm- Quality: The same quality, such as non-Guide to ATTRA’s ing system are willingness to experiment with certified seed or disease-free seed, of potatoOrganic Publications new or different farming practices and the seed is not available .Farm-Scale Composting ability to observe how management practices Quantity: The desired variety is not availableResource List influence the farm ecosystem. Talk with as in commercial quantities.Overview of Cover growers experienced in using sustainable Form: The same variety that you typicallyCrops and Green techniques to find what methods will work in grow is not available.Manures your region. This publication includes threeIntercropping Principles profi les of growers throughout the countryand Production who are producing organic potatoes. There If you source nonorganic seed due to anyPractices is also a list of experienced organic grow- reason listed above, you must document that ers in the Further resources section of you researched at least three different seedPrinciples of Sustainable this publication. These growers agreed to sources to fi nd organic seed and that theWeed Managementfor Croplands be a resource for new farmers or farmers same quality, quantity or form is not avail-Flame Weeding for able from those sources. Also, all non-cer-Agronomic Crops tified seed must be sourced as untreated if organic seed is not commercially availableNematodes: (King, 2006).Alternative ControlsColorado Potato Beetle: Another consideration when buying seedOrganic Options is ensuring that the seed is certified as disease free (Charlton, 2008). If certi-Farmscaping to fied disease-free seed is not available inEnhance Biological the organic form, seed can be purchasedControl from a nonorganic source as allowed inNotes on Compost Tea the quality stipulation of the National Organic Program (NOP, 2006). An excerpt from the National Organic Program regulations states: § 205.204 Seeds and planting stock Organic potato stock is required by the National practice standard Organic Program unless you demonstrate the same variety, quantity or quality is not available from an (a) The producer must use organically organic seed supplier. Photo by Neva Hassanein, grown seeds, annual seedlings and plant- courtesy of Community Food and Agriculture Coalition. ing stock, except that,Page 2 ATTRA Potatoes: Organic Production and Marketing
  3. 3. (1) Nonorganically produced, untreated has been granted in accordance withseeds and planting stock may be used to § 205.290(a)(2);produce an organic crop when an equivalent (4) Nonorganically produced planting stockorganically produced variety is not commer- to be used to produce a perennial crop maycially available, except that organically pro- be sold, labeled or represented as organi-duced seed must be used for the production cally produced only after the planting stockof edible sprouts; has been maintained under a system of(2) Nonorganically produced seeds and organic management for a period of no lessplanting stock that have been treated with than one year; anda substance included on the National List (5) Seeds, annual seedlings and plantingof synthetic substances allowed for use in stock treated with prohibited substancesorganic crop production may be used to may be used to produce an organic cropproduce an organic crop when an equiva- when the application of the materials is alent organically produced or untreated vari- requirement of federal or state phytosani-ety is not commercially available; tary regulations (2006).(3) Nonorganically produced annualseedlings may be used to produce an Fertility and nutrientorganic crop when a temporary variance management Potatoes have high nitrogen and potas- sium requirements. These can be met Certified seed and certified organic by using manures, compost and crop seed stock: What’s the difference? rotations, which are detailed in the later The Western Organic Potato Pest Manage- sections. You can assess soil nutrient ment Strategic Plan offers clarification to levels with a soil test. If nutrient levels some confusion about certified disease-free are deficient, apply organic amendments. seed. This excerpt from the plan explains the difference between certified disease-free Most organic potato growers should seed and certified organic seed stock: consider producing their crop with 120 pounds of nitrogen, 25 pounds of phosphate Certified disease-free seed stock: and about 140 pounds of potash per acre “It is important that organic potato growers (Sideman and Johnson, 2006). plant high-quality, early generation, certi- fied seed to manage diseases. Certification of seed does not guarantee that the seed Seed sources for organic potato production potatoes are disease free, but that the dis- ease levels fall within certain tolerable levels. This is only a partial list. Your local organic certification organization Certification means that the seed potatoes may know of local seed sources. have met the standards of a grower-sup- Wood Prairie Farm (207) 872-8317 FAX Notes: Organic potatoes, 49 Kinney Road www.fedcoseeds.com garlic and onions ported state certification agency. Seed pur- Bridgewater, ME 04734 Order: Mail, fax chased from different states and countries Catalog: Online, print Healthway Farms are subject to different certification rules. As 1-800-829-9765 request through Web site PO Box 49 1-800-300-6494 FAX or send $2. such, each certification agency has its own Malin, OR 97632 orders@woodprairie.com Quantity: Retail and set of tolerances, or allowable amounts, for wholesale (541) 723-4725 www.woodprairie.com each disease.” scott@healthwayfarms.com Order: Online, e-mail, fax, phone Ronnigers Potato Farm www.healthwayfarms. Certified organic seed stock: Catalog: Online, print 2101 2135 Rd, com/index.html “Certified organic seed is not necessarily certified Quantity: Retail and Austin CO 81410 Order: E-mail, phone at the same specifications required for certified wholesale (877) 204-8704 Catalog: Online, print Notes: Organic seed Quantities: Smaller disease-free seed that meets stringent disease and potatoes info@ronnigers.com quantities of certified virus-free specifications and other physiological www.ronnigers.com potato and organic requirements. Certified organic potato seed is FEDCO Seeds/Moose Order: Online, e-mail, fingerling seeds up to fax, phone 10 pounds. grown in accordance with the National Organic Tubers Catalog: Online, print Program regulations (Miller et al., 2008).” PO Box 520 Quantities: Up to 50 Waterville, ME 04903 pounds availablewww.attra.ncat.org ATTRA Page 3
  4. 4. Note that nutrient requirements vary by ble to other soil amendments, but no cur- potato variety and yield goals. Lowering the rent studies support this claim. Com- soil pH will help prevent common potato post that is available on the farm should scab problems, but not powdery scab. A soil be considered as a soil amendment. pH of 5.0 to 5.2 is recommended for pre- The ATTR A publication Farm-Scale venting scab, but this pH level may affect Composting Resource List has more other crops in the rotation, as well as nutri- information about this topic. ent availability (Charlton, 2008). Sulfur is an organically acceptable way Rotations to lower soil pH. Contact your local Coop- The most important step in organic potato erative Extension Service office to deter- production is planning a crop rotation mine the correct quantities to apply based scheme that allows a few years between on your current pH, soil type and region. potato crops on the same land. For Before purchasing any sulfur amend- organic production, a lengthy rotation ment, contact your certification agent from four to seven years generally assures to obtain a list of organically accept- good plant and soil health. A lengthy able sulfur amendments. Some amend- rotation also reduces long-term relianceN utrient requirements ments have inert ingredients that are not on expensive inputs and increases the acceptable by NOP standards. percentage of marketable potatoes. vary bypotato variety and The ATTRA publication Sustainable Longer rotations can be thought of as ayield goals. Soil Management provides information form of crop insurance because the rota- about nutrient management and ref- tions help prevent plant pathogens in the erences that are useful to the organic soil from building up to economically dam- grower. Please contact ATTRA at 1-800- aging levels. Growers must consider rota- 346-9140 if you would like a copy of this tion plans with crops that are not hosts for publication or search the ATTRA Web potato pathogens or insects. The key con- site at www.attra.ncat.org. sideration for the long-term viability of organic production is preventing problems Organic matter through maintaining good soil quality. You can organically manage nutrient requirements with animal manures and Rotat ions that include cover crops composted materials. Annual application have the advantage of adding organic of these materials can provide a well-bal- matter and nitrogen to the soil. This anced, stable form of nutrients and help generally will reduce input costs over build organic matter in the soil. time. Organic matter helps soils resist compact ion, a l lows for better root In a multiyear study of sustainable penetration, stores more soil moisture potato cropping systems, researchers and allows more water penetration. Cover from the University of Maine demon- crops and green manures may include strated yield increases with the applica- legumes, sudan grass and mustards. tion of 10 tons of compost per acre. The Mustards also have been shown to play researchers also studied the economic a positive role in soil pest management considerations of applying compost and (McGuire, 2003). determined that buying compost would require a price premium on potatoes to Useful characteristics for a cover crop make the compost purchase cost-effective or green manure in a potato rotation (Porter, 2002). include: This study predates recent increases • The abi l it y to tolerate frost in conventional fertilizer prices. The and grow well under cool fall cost of compost may now be compara- conditions;Page 4 ATTRA Potatoes: Organic Production and Marketing
  5. 5. • The ability to quickly produce substantial amounts of biomass as a weed suppressant; • The ability to fix nitrogen and suppress soilborne potato pests; • A compatibility with the manage- ment requirements of other crops in the rotation; • The availability of seed and a lack of planting restrictions, such as the restriction of rapeseed production in canola districts; and • The ability to avoid producing and shedding seed, which leads to problems with volunteer plants.A good rotation includes crops that arenot hosts to common potato pests. A goodrotation also includes green manuresthat add nutrients and organic matter tothe soil (Hutsinger, 1995). Mustards used in a rotation can be a disease and nematode management strategy. Photo byThe ATTRA publications Overview of Cover Peggy Greb, courtesy USDA/ARS.Crops and Green Manures and Intercrop-ping Principles and Production Practices second year, Porter uses an adaptedprovide more detailed information about potato planter to scrape the clover fromthese subjects. Small grains, corn and sor- the ridge and plants potatoes from 2 toghum sudangrass may benefit a potato crop 3 inches deep. One week later, he killsthat follows. In Maine, some growers have the clover with a f lail chopper to pre-used Japanese millet as a cover crop in the vent competition with the potatoes. Onlyyear prior to potatoes in an effort to reduce one hilling is required, occurring sixRhizoctonia. The skin of potatoes withthe Rhizoctonia fungus appears to weeks from planting time. A second coverbe covered in dirt that won’t wash off crop could be seeded at this time,(Grubinger, 2005). In parts of the West, although harvesting operations are notproducers rotate potatoes with mustard refined to assure survival of a covercover crops to prevent root knot nematode (Porter, 2006).and Verticilium outbreaks. More informa- Porter estimates that he saves fromtion about using mustard as a disease andnematode suppressant is provided in the $50 to $60 per acre in energy costs asNematode management section below. a result of reduced tillage. His research also assesses the nutrient savings thatDr. Gregory Porter at the University of result from the nitrogen-fixing legume.Maine developed a two-year reduced- He mentioned that wheat could betillage rotation for potatoes and barley. substituted for barley. For more informationThe rotation uses red clover as a covercrop. Porter builds planting ridges in the on Porter’s research, see the final report ofspring of the fi rst year of the rotation and their Sustainable Agriculture Research andthen seeds the entire field to barley and Extension Project Report, Soil Amendmentred clover. He harvests barley in the fall and Crop Rotation Effects on Productivityand allows the red clover to continue as a and Soil Properties within Potato Productionwinter cover. In the spring of the Systems under Further resources.www.attra.ncat.org ATTRA Page 5
  6. 6. Table 1: Potato rotation chartLocation Rotation sequence Comments Contact/referencePacific 7-year crop rotation: Year 1-3: Alfalfa; This rotation works well under Mike HeathNorthwest Year 4: Row crop*; Year 5: Grain; organic production practices. (208) 539-4107 Year 6: Row crop*; Year 7: Grain Buell, ID * Dry beans, squash, potatoes and field corn are row crop options depending on marketMichigan 2-year rotation: Year 1: Potato and Research in MI has shown that poul- Annual report (2005) of the then rye planted as winter cover; try compost added to the soil under Southwest Michigan Research Year 2: Snap bean. these two-year conventional rota- and Extension Center. 3-year rotation: Year 1: Potato and tions in combination with use of www.maes.msu.edu/ then rye/vetch planted as winter cover crops can increase soil quality swmrec/publicationsfolder/ cover; Year 2: Corn; Year 3: Wheat and at least maintain yields com- Annualreports/05annualrpt/ and then clover pared to no cover crops. The three- snappenvfriendveg.pdf year rotation had a marketable yield nearly the same as the two-year rotation for comparing single har- vest years, but less than half of the scab of the two-year rotations.Maine 4-year rotation: Year 1: Potatoes; This rotation is used for organic Jim Gerritson Year 2: Spring wheat or oats, under- seed potatoes. Wood Prairie Farm sown with clover or timothy grass; www.woodprairie.com Year 3: clover sod, plowed down, year 4); Year 4: Buckwheat, plow down and then plant rapeseed as biofumigantMaine 3-year rotations, various crops : This research on various three-year Robert P. Larkin and Year 1: Soybean/sweet corn/green rotations that all included potato C. Wayne Honeycutt bean/canola; Year 2: Canola/soy- found that continuous potatoes U.S. Department of Agricul- bean/sweet corn/ barley and then decreased soil microbial activity. ture – Agricultural Research clover; Year 3: Potato Overall microbial activity were high- Service, New England Plant, est following barley, canola and Soil and Water Laboratory sweet corn. Potato crops following Orono, ME 04469 canola, barley or sweet corn provided (207) 581-3367 the lowest levels of Rhizoctonia dis- bob.larkin@ars.usda.gov ease and best tuber quality, whereas (207) 581-3363 potato crops following clover or soy- wayne.honeycutt@ars.usda.gov bean resulted in disease problems in some years. 3-year rotations: These rotations are used on a 200- Igl FarmsWisconsin Year 1: Potato; Year 2: White oats acre organic farm. Antigo, WI underseeded with clover; Year 3: *Peas are determinant grain pea, not a (715) 627-7888 Field peas*; forage pea, and can be used directly as iglfarms@verizon.net or animal feed without processing. Year 1: Potato; Year 2: Oats underseeded with clover; Year 3: AlfalfaCanada 2-year rotation: Year 1: Potato and then rye planted as winter cover; Year 2: Spring cereal with legume underseeding, legume incorporated before potatoPage 6 ATTRA Potatoes: Organic Production and Marketing
  7. 7. It is important to note that legumes such simply because there are so many fac-as peas, beans and crimson clover are tors that influence the choice of rotations,hosts to some races of Rhizoctonia (Cer- including economics of the crops in theesini, 1998) and can encourage scab in rotation, available land, weather andcertain regions. Red clover may be a host climate, farmer skills and knowledge,of Rhizoctonia as well. pest management and soil quality goals.As often happens in agriculture, there Since many of these factors are movingis no clear-cut answer to the question of targets, implementing a good crop rotationwhat rotation a farmer should use. It is a is as much an art as a science because somatter of evaluating the costs and ben- much depends on the knowledge, skill andefits of a particular practice or combina- creativity of the farmer.tion of practices. In this case, producersmust weigh the risk of these crops host- When making rotation decisions, it ising and possibly increasing Rhizoctonia helpful to have additional informationagainst the soil fertility advantages and from local experts — be they farmers,other benefits of planting a legume. extension agents or researchers — whoTable 1 (page 6) provides some exam- know about the pest pressures and soilples of potato rotations used around the and climate considerations for yourcountry. It is not meant to be exhaustive, particular region.www.attra.ncat.org ATTRA Page 7
  8. 8. Section II Weed management Organic potato producers control weeds largely by cultivation. Good field preparation, timely pest control and proper seed spac- ing provide a satisfactory stand that can also reduce weed competition. In areas with lots of weed pressure, farmers should choose specific potato varieties that put on a canopy quickly. Hilling, either with an implement or by hand, is a good way to control weeds and is a neces- sary component of potato production. In larger operations, an implement called the dammer- Root knot nematodes are common in Western organic potato systems and are the leading cause of soil fumi- diker hills and cultivates at the same time. gation in commercial potato production in the North- Complete all hilling by the time the plants are west. Photo by Jack Kelly Clark. Courtesy University of Contents 10 inches high (Sideman and Johnson, 2006). California-Davis Statewide IPM Program.Section II: Your chances of stolon pruning are high afterWeed management .............9 the plant reaches 8 inches. Stolon pruning is a et al., 2005). For more details on theseNematode management ...9 condition that causes the underground stems techniques, refer to the ATTRA publi-Disease management ..... 10 Early blight ....................... 10 to die-back, reducing yields and increasing cations Principles of Sustainable Weed Late blight .........................11 disease incidence. (Charlton, 2008). Management for Croplands and Flame Rhizoctonia ........................12 Cover cropping is also a good way to Weeding for Agronomic Crops.Insect management...........14 Colorado potato beetle14 reduce weed populations in your soil and Potato leafhopper ..........18 add soil organic matter. Results from the Nematode management Neem ...................................18 Maine Potato Ecosystem Project demon- Nematodes are microscopic roundworms strate that cover cropping with red clo- found in many habitats. Nematodes are ver and adding soil amendments such as the most abundant multicellular organ- compost and manure reduced weeds and isms on Earth. Most are beneficial enabled the potato crop to better compete members of their ecosystems, but a few with weeds (Porter, 2002). Fast-growing are economic parasites of plants. The cover crops such as buckwheat and sor- Columbia, stubby and northern root ghum sudan grass add organic matter and knot nematodes are common in Western compete with weeds. For smaller farmers, organic potato systems and are the lead- mulching with clean straw is an option that ing cause of soil fumigation in commercial builds soil organic matter and helps with potato production in the Northwest. weed populations. Root knot nematode feeding reduces the Flame weeding is another technique used vigor of plants and causes blemishes on by some growers. Flaming is also used in tubers (Westerdahl, 2007). Infection of management of the Colorado potato beetle. tubers by the Columbia and stubby root Stale seed bedding draws down the weed knot nematode often results in the for- seed bank. Irrigate or wait until after a rain mation of galls that appear as knobs or to let weed seeds germinate, and then flame swellings on the tuber surface and affect weed or cultivate. Crop rotation is another marketability. Root knot nematode lar- measure that helps keep weed problems vae invade roots or tubers, establish from becoming severe (Gallant, 1998). feeding sites and develop into the adult Producers can also significantly reduce stage. Adult females are swollen, seden- weed populations by using a drip irriga- tary and lay eggs in a gelatinous matrix tion system combined with bed planting on or just below the root surface. These instead of sprinkler irrigation (Mirabelli eggs hatch and larvae invade other rootswww.attra.ncat.org ATTRA Page 9
  9. 9. and tubers. Feeding by root knot nema- these varieties, see the ATTRA publication tode eliminates the possibility of expor- Nematodes: Alternative Controls. tation since infected potatoes are banned in many countries. Disease management There are recent promising develop- Organic management of viral, bacterial and ments with biofumigation using bras- fungal diseases begins with using certified sica mustard cover crops in a rotation seed, employing proper sanitation prac- before potatoes. Brassica crops such as tices, controlling other plant and insect rapeseed and mustard contain active vectors and using crop rotations. The two chemicals called glucosinolates. The integrated pest management (IPM) guides breakdown of these chemicals has been listed in the Pest management portion of shown to suppress some soilborne dis- the Further resources section cover these eases, nematodes and weed seeds. The topics. What follows is a brief summary of best strategy for the ultimate suppres- the diseases that are the most troublesome sion of soilborne diseases and nema- to organic potato growers and some preven- todes is selecting a species of mustard tative and control measures. that produces large amounts of biomass and glucosinolates. Also, before incor- porating, chop the green manure with Early blight (Alternaria solani) a rotary mower or a high-speed f lail Early blight is basically a disease of chopper. The breakdown of the biofu- older plants or plants that experienced migant seems to be better in moist soils, stress, such as infection by some other so irrigate following incorporation or plant pathogen or deficiencies of nitrogen time incorporation to occur with a rain or water. Excessive irrigation can also (McGuire, 2003). cause susceptibility. The lower leaves of the plant are generally infected fi rst. Jack Brown, a plant breeder specializing Early blight may appear early in the in brassicas at the University of Idaho, season, but the rate of infection accel- has released two biofumigant varieties: erates rapidly after f lowering. Tomato Humus rapeseed and IdaGold mustard. and other solanaceous plants are hosts Each variety contains elevated levels of to early blight. The disease has also glucosinolates. For more information on been reported on other plants such as some brassicas. There are several races of this pathogen. Some races are highly pathogenic while others are saprophytic and live in the soil on dead organic mat- ter. The pathogen can survive on crop debris, as a saprophyte in the soil, in infected tubers and on other hosts. The most severe damage generally occurs on early maturing potato variet- ies. However, some varieties within each maturity group have greater resistance to foliar infection by early blight. Infec- tion begins as small dark brown spots on lower leaves. As the infection spreads, the spots are restricted by the leaf veins and take on an irregular, angular look.Severe early blight symptoms. Photo by Cynthia M. Ocamb, courtesy Oregon State Close inspection of the infection willUniversity. reveal a series of dark, concentric linesPage 10 ATTRA Potatoes: Organic Production and Marketing
  10. 10. within the infected area. These lesions Table 2: Susceptibility to early and late blight.will enlarge and may coalesce as thedisease progresses. Tubers may also Highest Lowest susceptibility susceptibilitybecome infected and will have irregular-shaped, sunken lesions with somewhat *Note: Certified seed for some of these varieties may not be available.darker borders. The infection is shallow Early- and mid- Late-season Very lateand causes a brown discoloration of the season cultivars cultivars cultivarstuber flesh. These lesions can increase in Norland Russet Buttesize during storage and reduce the mar- Redsen Burbank Nooksackketability of the crop. Lesions are mosttroublesome on white, red-skinned and BelRus Kennebic Ontariochipping varieties. Norchip Katahdin Norgold RosaGrowers should select a marketablecultivar with the greatest resistance to Russetearly blight. Table 2 lists the suscepti- Early Gembility of several cultivars. The cultivar Superiorshould also fit in with other aspects of Mononaan IPM program. Water management for LaChipperearly blight prevention walks a thin line.Too much water will leach soil nitrogen. AtlanticNitrogen and phosphorus deficiencies Table adapted from: (Stevenson, 1993).can create susceptibility to early blight, Lowestbut too much nitrogen can reduce crop susceptibilityyields and delay maturity. to early and late blightGrowers should closely monitor soilferti lity, especially nitrogen levels.This can be done with petiole analysis. compost extract prepared in a 1:5 ratioInsufficient soil moisture will stress the of compost to water (volume: volume)plant and cause early senescence. This provided a level of early blight controlis a condition conducive to early blight similar to that of copper fungicide treat-development. Overhead irrigation cre- ments (Lahkim, 1999). It should be notedates ideal situations for infection and the that compost teas can be highly variablespread of foliar pathogens such as early and inconsistent. Commercial compost teasand late blight. Pay close attention to the may provide more consistency. For morefrequency, duration and timing of irri- information on making compost tea on yourgation during possible infection peri- farm, see the ATTRA publication Notes onods, since too much water can lead to Compost Tea.early and late blight. Overhead irriga-tion should be timed so plants dry prior Late blightto dew formation in the late evening andearly morning. Also, the plants should (Phytophthora infestans)also be allowed to dry early in the morn- Late blight is the most serious fungaling, prior to the start of irrigation. disease of potatoes worldwide, according to the authors of Integrated Pest ManagementA 1994 study concluded that compost for Potatoes in the Western United Statesteas can be as effective as copper fun- (Strand, 2006).gicide treatments to reduce diseasesymptoms. The study examined the use New, more virulent strains of late blightof compost teas for controlling early cause serious losses in potato varietiesblight. Results of this study indicate previously considered resistant to the fun-that spraying the plants with 14-day-old gal disease. Late blight is usually of littlewww.attra.ncat.org ATTRA Page 11
  11. 11. blight. Recent studies from the OSPUD farmer participatory research project at Oregon State University show promising late blight management using compost teas and Oxidate, a hydrogen dioxide and peroxyacetic acid product from BioSafe Systems, a manufacturer of biodegrad- able disease-control products. Some commercially available U.S. potato varieties that demonstrate resistance to late blight are the New York 121, a mid- to late-season variety; two Hungarian Sarpo varieties: the Sarpo Mira, a medium- to late-tablestock and the Sarpo Axona, a processor potato; and Remarka, an a l l-pu r pose potato ( Per r y, 20 02 ). Defender is a new late blight-resistantLate blight in potato tuber. potato cultivar that was released in Idaho,Photos by Neil C. Gudmestad, Oregon and Washington by the Tri-Statecourtesy North Dakota State Potato Variety Development Program inUniversity. 2004. Useful levels of fi eld resistance to both late blight and early blight were observed in Defender in the absence of fungicide sprays and reduced fungicide input programs (Stevenson et. al., 2007). Rhizoctonia (Black scurf, Stem canker, Rhizoctonia solani) Rhizoctonia is a pathogen present in all potato-growing areas. Most damage occurs concern in the western United States, during the early part of the growing sea- except in the coastal valley regions where son, particularly when infected tubers are late blight occurs regularly. Its occur- planted. Cold, wet soils can increase prob- rence in other regions of the United States lems with this disease. is dependent on both the presence of the pathogen and cool, damp weather. The fungus survives in the soil either as Blight forecasting still occurs quite mycelia associated with decomposing plant regularly to help alert growers when residues or as sclerotia, the dirt that won’t conditions are conducive to the disease. wash off unharvested tubers. Soilborne For more information on blight fore- infections, known as the chronic phase casting, contact your local Cooperative of the disease, generally will not infect Extension System office. sprouts. Instead, soilborne infections cause a decrease in tuber quality and yield by Sanitation is the best defense against pruning tubers and causing reddish-brown late blight. Eliminate all cull piles and lesions that may develop into cankers. control volunteer potato sprouting the following spring in areas where there was Tubers may also be malformed, cracked, an incidence of late blight. pitted or display stem-end necrosis. Young plants that develop from infected Copper products are currently allowed by seed pieces are most severely affected. NOP standards and are the most effective Sprouts may be completely girdled by means of controlling and preventing late lesions and killed. Partially girdled stemsPage 12 ATTRA Potatoes: Organic Production and Marketing
  12. 12. will slow growth and development and mayresult in stunting and rosetting of plant tops;purple pigmentation of leaves; upward leafroll; and chlorosis, which is usually mostsevere at the top of the plant.Potato growers can manage Rhizoctonia withmonitoring. It is useful to keep good recordsof the existence and severity of black scurfproblems in each field. This way, fields witheconomically damaging levels of black scurfcan be managed through appropriate rota-tions and other methods.Cultural controlsAvoid growing sugar beets prior to pota-toes because sugar beets tend to increase Rhizoctonia (Black Scurf) in tubers of potato. Photo by Neil C. Gudmestad, courtesyRhizoctonia problems. Avoid a rotation North Dakota State University.with buckwheat before potatoes becauseRhizoctonia colonizes mature buckwheat surface of tubers under cool, moist condi-stems (Leach and Specht, 1987). Crop tions, usually after the vine starts to die.rotation to nonhost crops such as cere-als for at least two years can reduce Biological management optionsdisease incidence. A three- to fi ve-year Research in greenhouses and in therotation away from potatoes is recom- field shows that dusting seed pieces withmended if disease incidence is severe fungal antagonists of Rhizoctonia can(BASF Canada, 2005). significantly reduce stem canker andIt should be noted that recent protein- and black scurf (Beagle-Ristaino and Papavi-DNA-based studies of Rhizoctonia found zas, 1985). This reduces Rhizoctoniaconsiderable genetic diversity in Rhizocto- infection and decreases the viability ofnia and its hosts (Ceresini, 1998). Grow- sclerotia on the potato. The commerciallyers should be careful when selecting rota-tion crops. Generally speaking, cereals area safe bet. Crops closely related to potatoes, Cultural management optionssuch as tomatoes, eggplants and peppers, for Rhizoctonia:along with volunteer potatoes, may host Rhi- • Plant potatoes when soilzoctonia and should not be used in a potato temperature is above 60rotation. Likewise, related weeds such as degrees Fahrenheit.black nightshade and Jimsonweed should • Avoid irrigation before thebe kept out of the field. expected harvest.Planting certified seed significantly • Plant seed pieces no morereduces poor stands and sprout death than 2 inches deep. Theassociated with Rhizoctonia. For a defi ni- temperature of the soil istion of certified seed, see the box on page warmer at this depth.three. However, using certified seed will • Harvest potatoes as soon asnot eliminate Rhizoctonia problems since skin set occurs after vine kill tothe fungus survives in the soil either as avoid development of sclerotiamycelia associated with decomposing plant on mature tubers in the soil (Rowe et al., 1995).residues or as sclerotia on unharvestedtubers. The sclerotia may form on thewww.attra.ncat.org ATTRA Page 13
  13. 13. available fungal antagonists featured Insect management in the study include Trichoderma viride and Trichoderma virens. There is a list Colorado potato beetle of commercial products formulated with (CPB, Leptinotarsa decemlineata) fungal antagonists of Rhizoctonia, as well as contact information for manufac- Many insect pests are associated with potato turers of the microbial pesticides, in the production. Because the Colorado potato Fur ther resources section of this beetle (CPB), Leptinotarsa decemlineata, is a major insect problem in potatoes, we focus publication. The ATTRA publication on acceptable approaches to control this pest Biointensive Integrated Pest Management in organic production. The ATTRA publica- has more information on using fungal tion Colorado Potato Beetle: Organic Control antagonists. Options provides more detail about managing Many scient i f ic invest igat ions have this pest. ATTRA also has information about examined various aspects of biologi- control techniques for other pests, such as cal control of Rhizoctonia (Jager and the blister beetles and aphids. Velvis, 1986; Lewis and Papavizas, 1987; Howell, 1987). More recent research shows that some readi ly ava i lable commercial biocontrol products reduce the development of stem lesions in the field, with control comparable to that of a standard chemical treatment. However, no treatments, including chemi- cal control, substantially reduced black scurf on potato tubers. Some treatments resulted in higher total yield, as well as Immature Colorado potato beetle. Photo by Tom Murray. higher yield of larger potatoes. Although no treatments effectively controlled black scurf, all biocontrol treatments controlled stem canker and some resulted in greater overall yield and larger potatoes (Larkin and Talbot, 2002). Recent studies in Washington show that mustard green manures may offer farm- ers an equally effective but less expen- sive alternative to fumigants for control Adult Colorado potato beetle. Photo by Tom Murray of soilborne pests (McGuire, 2003). The fi ndings from this study suggest poten- tial for mustard green manures to replace the fumigant metam sodium for potato production in some cropping systems. The practice can also improve water infi ltration rates and provide substantial savings for farmers. While Rhizoctonia is not mentioned in the above study, another Colorado potato beetle eggs are bright orange and recent study found that mustard biofumi- typically located on the undersides of leaves. gants reduced incidence of Rhizoctonia in Photo by Whitney Cranshaw, courtesy Colorado a greenhouse setting. State University.Page 14 ATTRA Potatoes: Organic Production and Marketing
  14. 14. The CPB is native to the United States. Its A combination of several strategies can helporiginal range was restricted to the east- keep CPB populations under control. Cropern part of the Rocky Mountains. In the rotation, preferably with field corn, wheatRockies, the beetle fed on buffalo burr, or some other crop that can tolerate a pHa plant of no economic importance. Once of 6.0, can delay CPB population buildup.the potato was introduced to this region, Ideally, rotated fields should be isolatedthe beetle moved to the crop and spread from the previous year’s potato planting.eastward from potato patch to potato patchand reached the East Coast by 1874. The Cultural techniques to managebeetle is now found throughout North Amer- the CPBica, except in parts of Florida, Nevada, The effect of crop rotation on populationsCalifornia and eastern Canada. By 1935 of CPB and on the incidence of early blightthe CPB was established in France and is caused by Alternaria solani is quantified innow widespread in Eurasia. a 1994 study (Weisz). The study noted thatThe CPB is the most economically threat- infestations of both pests are inversely relatedening pest of potatoes in the northeastern to the distance between rotated fields and theUnited States. If left uncontrolled, this pest nearest location where potatoes were planted T hecan completely defoliate a potato crop by late in the previous season. In other words, the ColoradoJuly (Hollingsworth et al., 1986). Although farther you plant this season’s potatoes from last season’s potato field, the fewer pest prob- Potato Beetlethe potato is its favorite food, the beetle mayalso survive on tomato, eggplant, tobacco, lems will occur. is also the mostpepper, ground cherry, thorn apple, Jimson- economically Research at Cornell University demon-weed, henbane, horse nettle, belladonna, strated the efficacy of flame technology in threatening pestpetunia, cabbage, thistle, mullein and other controlling overwintering CPBs. The most of potatoes in theplants (Metcalf and Flint, 1962). The CPB effective time for flaming is between plant northeasternis resistant to most registered pesticides, emergence and when the plant reaches 8 United States.making the beetle one of the most difficult inches in height. Taller plants are less heatinsect pests to control in cultivated crops tolerant and their canopy shields many(Hollingsworth et al., 1986). of the pests. The best control is achieved on warm, sunny days when beetlesThe life cycle of the beetle varies accord- are actively feeding on top of the plants. Ining to where it is found. In northern Maine, trials, flaming provided 90 percent controlthe CPB completes one generation per year. of overwintering adult CPBs, contrastedFarther south, the CPB completes three with from 25 to 50 percent with chemi-generations per year. The adult beetle over- cal insecticides. Flaming also reduced eggwinters in the potato field, from 12 to 18 hatch by 30 percent (Moyer, 1992).inches below the soil surface and in pro-tected sites around the field. The beetles The CPB ca n be excluded f romemerge in late spring, move to the field and crops with the use of floating row covers.mate once established on a plant. Females Floating row covers are thin fabrics spunlay egg masses on lower leaf surfaces in from a synthetic material. The productbatches of approximately 25 eggs. A single allows air and moisture to pass throughfemale may lay up to 500 eggs. Because the while preventing pest species access toeggs are laid in clumps, the larvae tend to the plants. The floating row covers shouldbe found in clumps rather than randomly be put on either shortly after plantingthroughout the field (Hollingsworth et al., or emergence.1986). You can fi nd good life cycle infor- Straw mulch of wheat or rye in potatomation for the CPB in the book Destructive fields may reduce the CPB’s ability toand Useful Insects, by Metcalf and Flint, locate potato fields and alter the microen-1962. The book is available from most vironment in favor of CPB predators (Brust,agricultural libraries. 1994). In the fi rst half of the season, soilwww.attra.ncat.org ATTRA Page 15
  15. 15. predators — mostly ground beetles — climb field borders or by planting insectary strips potato plants to feed on second- and third- in the field can increase the effectiveness stage instar larvae of the CPB. In the sec- of these biological controls. ATTRA has ond half of the season, lady bird beetles more information on this technique in and green lacewings are the predominant the publication Farmscaping to Enhance predators and feed on eggs and fi rst and Biological Control. second instars. The increased number of Several plants, such as tansy and catnip, predators in mulched potato plots com- are reported to repel the CPB. Two jour- pared to non-mulched plots resulted in sig- nal abstracts from The IPM Practitioner nificantly less defoliation from the CPB and discuss interplanting trials conducted at one-third higher tuber yields. Rodale Institute Research Center in coop- eration with USDA researchers (Olkowski, Varietal resistance to the CPB et al., 1992). The experiments show tansy Some potato varieties, such as Russet and catnip were from 58 to 100 percent Burbanks, seem to be more tolerant to effective in repelling the CPB from pota-S ome potato varieties, the CPB, but no varieties are completely toes. However, a European study shows that resistant. The April 1989 issue of National companion planting did not significantly such as Russet reduce plant defoliation by the CPB. In the Gardening highlighted research on plantingBurbanks, seem to be early maturing varieties that develop potato European study, companion plants weremore tolerant to the tubers before CPB populations explode. smaller than the potatoes in the begin-CPB, but no varieties It listed seven varieties that mature from 75 ning of the season. The study’s authorsare completely to 88 days. The varieties are the Caribe, speculated that more mature companion Norland, Pungo, Redsen, Sunrise, Superior plants might be more effective (Moreau etresistant. and Yukon Gold. The issue also illustrated al., 2006). In 1992, The IPM Practitio- the growth stages of the potatoes and how ner published a special report specifically the stages coincide with CPB emergence addressing potato IPM for the CPB. The and larval development (Ruttle, 1989). This issue can be ordered as a photocopy from the publisher. See the Further resources practice of using early maturing varieties section for ordering information. may prove beneficial to growers in northern regions of the United States, where cooler Parasitic nematodes are another con- temperatures slow insect development. trol option. Commercial formulations of Heterorhabditis species are available and Biological controls of the CPB have been shown to be more pathogenic (Berry, et al., 1997) to the CPB than Stein- There are several natural enemies of the ernema species, which is also commercially CPB, but these enemies are rarely seen available. The Ohio State University Web in commercial potato fields because of site portal for beneficial nematodes, avail- heavy pesticide use. Even under organic able at www.oardc.ohio-state.edu/nematodes, growing conditions, when natural enemies provides helpful information on how to use are abundant, the beetle can still cause and where to obtain beneficial nematodes. defol iat ion. The genera l predators, such as lady bird beetles, lacewings and Biorational controls for the CPB stink bugs, provide some control of the CPB, as do several parasites. Dorypho- Commercially available M-One is a prod- rophaga doryphorae and D. coberrans, two uct manufactured by the Mycogen Corpora- species of fly that invade the larvae; and tion of California. See contact information in Edovum puttleri, a wasp that parasitizes the Further resources section for order- ing information. This biopesticide is made CPB eggs; were recently introduced and from Bacillus thuringiensis (Bt) var. ‘San are commercially available. Diego’, a naturally occurring bacterium, Increasing habitat for natural enemies by and is effective for controlling CPB with- providing pollen and nectar sources along out disrupting beneficial organisms. It is,Page 16 ATTRA Potatoes: Organic Production and Marketing
  16. 16. however, a genetically engineered product materials will work best in situations withand is not acceptable in organic certification moderate to high relative humidity.programs. Entrust is a new formulation of SpinosadSome research indicates that sprays of manufactured by Dow AgroSciences. It isBacillus thuringiensis species tenebrionis registered for use on organically managed(Bt) will cause significant mortality of CPB farms to control the CPB and is popular withlarvae upon emergence from their eggs. organic farmers. The contact information toThis is because the beetles gnaw out of find a distributor near you is listed at the endthe eggs and continue eating the shells of this publication in the Further resourcesafterward, therefore also ingesting Bt section.particles (Ghidiu et al., 1994). Several neem-derived products areMycotrol-O, a formulation of the parasitic registered for use against the CPB.fungus Beauveria bassiana, is available from Soft-skinned larvae of CPB are reportedlyLaverlam International, based in Butte, killed on contact. In a two-year study of vari-Mont. This product is an effective control of ous organic techniques for controlling CPBthe CPB by itself or when used in combina- in the United Kingdom, a 2-percent formula-tion with Bacillus thuringiensis var. tenebri- tion of Neemix increased yield and loweredonis (Jones, 1999). Some formulations use beetle densities and the occurrence of defo-different strains of B. bassiana. Each strain liation significantly.has the greatest efficacy against a slightly The ATTRA Biorationals: Ecological Pestdifferent group of insects, so be sure to read Management Database, available at www.attra.the label or ask a sales representative about ncat.org/attra-pub/biorationals/biorationals_which formulations are most effective against main_srch.php, lists several organically accept-the CPB. Since these are all formulations able biorational pest management materials forwith a fungus as the active ingredient, the the CPB. Several of these materials are listedTable 3:Reduced Risk Pest Management Manufacturer Active ingredient OMRI listed*Agroneem Agro Logistic Systems Azadirachtin YesAgroneemPlus Agro Logistic Systems Azadirachtin YesEcozin AMVAC Chemical Corp. AzadirachtinOrnazin AMVAC Chemical Corp. AzadirachtinBiorin Biotech International Beauveria bassianaAzatin XL Plus Certis USA, LLC AzadirachtinNeemix 4.5 Certis USA, LLC Azadirachtin YesDiatect V Diatect International Diatomaceous Earth (Sili- con Dioxide)Conserve sc turf and ornamental Dow AgroSciences LLC SpinosadEntrust Dow AgroSciences LLC Spinosad YesSpintor 2sc Dow AgroSciences LLC SpinosadSuccess Dow AgroSciences LLC SpinosadFortune Aza Fortune Biotech Limited AzadirachtinPyola Gardens Alive!, Inc. PyrethrinsAnti-pesto-o Holy Terra Products, Ltd. Azadirachtin* OMRI is the Organic Materials Review Institute. If a product is OMRI approved, it is allowed for use in certified organic sys- tems. Contact your certifier before using any organic pesticide to ensure it is approved by the National Organic Program.www.attra.ncat.org ATTRA Page 17
  17. 17. above in Table 3. The database also provides selective. Anagrus species of trichogrammatid information about using cultural controls to wasps might be available at a local insectary prevent pest problems. and are effective against leafhopper eggs in inundative releases. Potato leafhopper Even if this particular species is not avail- (Empoasca fabae) able, you might consider an inundative The potato leafhopper, Empoasca fabae, does release of a generalist Trichogramma egg not overwinter in the northern United States parasite, as Trichogramma species tend and must migrate annually. The potato leaf- to parasitize whatever eggs are available. hopper is one of several closely related leaf- Make sure you check with the insectary hoppers in this genus. The potato leafhop- about parasite host ranges. Other benefi- per feeds on more than 200 cultivated and cial insects are green lacewing, lady beetle, wild plants including beans, potatoes, egg- minute pirate bug, assassin bug, syrphid fly, plant, rhubarb, celery, dahlia, alfalfa, soy- hover fly, robber fly, spiders, damsel bugs beans, clovers and sweet clover. A high and big-eyed bugs. migration rate and wide host range make control of the potato leafhopper difficult. The Department of Pesticide Regulation, part of the California Environmental Both nymphs and adults feed on the under- Protection Agency, publishes a booklet sides of potato leaves. By extracting the sap, called Suppliers of Beneficial Organisms potato leafhoppers cause stunting and leaf in North America. The most recent curl. Potato leafhoppers also bring on hop- version, from 1997, lists 143 commer- perburn, a disease caused by the injection of a toxic substance. Hopperburn is charac- cial suppliers of more than 130 beneficial terized by a yellowing of the tissue at the tip organisms used for biological control. It is and around the margin of the leaf. The yel- available for free download at www.cdpr. lowing increases until the leaf dies. Symptoms ca.gov/docs/ipminov/bscover.htm. are sometimes confused with drought stress (Bennett et al., 2007). Neem Neem works best when ingested by pests The ATTRA publication Farmscaping to and is effective for controlling leaf-eating Enhance Biological Control describes how to pests. Although neem is not effective for design your farm to favor predatory organ- controlling sucking insects such as leafhop- isms. These techniques can be integrated in pers, it appears that it still could be part a biointensive IPM program and can help of a biocontrol strategy targeted against the make your cropping system friendlier to insect. Neem shows considerable anti-feed- beneficial organisms. ant and growth-regulating effects on leaf- Biological control hopper nymphs (National Research Coun- cil, 1992). Neem is primarily an insect Leafhoppers have several growth regulator and should be applied parasites and predators. early in the crop cycle. It is essential to get The mirid bug, Cyrtorhinus good leaf coverage and to see that the neem species and specifically product adheres to the leaf surface. If not, Cyrtorhinus lividipennis, the nymphs, which feed on the undersides is an effective predator. of the leaves, will not contact the active Some members of the ingredient. The nymphs should be targeted wasp family are parasites because leafhoppers are most vulnerable in of leafhopper eggs. Some this stage. species of TrichogrammaPotato leafhoppers cause hopperburn, a disease are generalist egg para- The IPM Practitioner notes that gar-with symptoms that are sometimes confusedwith drought. Photo by Art Hower, courtesy sites and have a wide host lic sprays can signif icant ly reducePennsylvania State University Department of range. Other species of leaf hopper populations, although theEntomology. Trichogramma are more resulting numbers are still unacceptablyPage 18 ATTRA Potatoes: Organic Production and Marketing
  18. 18. high. Garlic may increase the efficacy of these interspecies crosses, including Kingother leafhopper pest management strat- Harry, protect themselves from pests byegies. Insecticidal soap penetrates the arming their leaves and stems with hairsinsect’s cuticle, disrupts the cell mem- fi lled with sticky fluids. These trichomesbranes and causes death by dehydration. explode when touched, miring small insectsThis method is likely to work best against such as leafhoppers and flea beetles innymphs (Olkowski et al., 1992). Efficacy is goo. The trichomes also ruin the appetites ofvariable with this method as well. hungry Colorado potato beetles, reducing or eliminating the need to use other pest controlAlternatively, a water spray directed at the measures (Pleasant, 2007). King Harryplant, especially under the leaves, will seed potatoes are available in limited quan-wash off the insects. This treatment is not tities from Wood Prairie Farm in northernrecommended in humid weather because of Maine. See the Potato seed stock box onpossible disease problems. Take care not page 3 for more information.to use excessive force. Spray early in themorning, especially in hot weather (Bradleyand Ellis, 1992). Other physical controlsinclude the use of floating row covers dur- OSPUDing the first month to keep leafhoppers out. A new kind of research andPyrethrin, rotenone and sabadilla are rec- information sharingommended only as a last resort. Rotenone is Eleven organic farmers in Oregon and Washington are workingnot approved by the NOP standards and has closely with Oregon State University faculty members to improveheavy restrictions from the Environmental potato quality and profitability through a participatory learningProtection Agency. process and on-farm, farmer-directed research.A new variety of potato called King Harry, This project encourages an exchange of existing knowledge of integrated management techniques and promotes farmer inno-and the earlier Prince Harry, are the result vation. OSPUD’s goal is to learn more about the wide variety ofof three decades of work by Cornell Uni- management issues, including soils, nutrients, insects, diseases,versity potato breeder Bob Plaisted. The weeds, tuber quality and profitability, facing small organic potatopotatoes have shown resistance to small farmers in the Northwest.insects such as leafhoppers and flea beetles. This project has generated a number of useful publications forStarting in the late 1970s, Plaisted began organic potato production. For more information and access tocrossing Katahdin and other mainstream these publications, visit http://ospud.org.varieties with Solanum berthaultii, a wildpotato from Bolivia. The most successful ofwww.attra.ncat.org ATTRA Page 19