Disease Management in Organic Vegetables

1. Disease Management in Organic Vegetables Sally Miller Department of Plant Pathology Tri-State Organic IP Video Program Session III April 19, 2007

2. Organic Disease Management • Importance of diseases varies among crops, locations • “Diseases are the Achilles heel of organic tomato production” Diver, Kuepper & Born 1995 • Management requires an integrated [systems] approach

3. Choose the Best Site • Well-drained fields • Water molds Pythium, Phytophthora • Good air movement • Promote rapid plant drying • Physical separation from other crops • Potatoes: late blight • Peppers: bacterial leaf spot • Conventionally produced crops

4. Improve Soil Quality • Reduce diseases by soilborne pathogens • Enhance composition of “beneficial” organisms • Increase the abundance and diversity of the soil microbial community • Increase soil organic matter • Cover crops/Green manures • Composts/Animal manures 

5. Effects of Compost on Plant Health • Increases soil suppressiveness to diseases • Induces disease resistance (“healthier plants”) • Improves soil tilth • Improves soil moisture-holding capacity High Tunnel Tomato

6. Good Quality Compost • C:N ratio 30:1 at the beginning • Finished compost C:N ratio = ~10:1-14:1 • 90-120 days • Temperature 131-170F, 3 days in a static aerated pile or 15 days in a windrow • Temperature> 15F above ambient indicates unstable compost • Turn to assure entire pile reaches 131-170F

7. Maximizing Disease Suppression • Compost • Cure 4 or more months • Incorporate into soil several months before planting • Inoculate with beneficial microorganisms, e.g. Trichoderma • Application • 5-10 tons (dry weight)/A - rule of thumb • Apply every year until significant organic matter improvement observed; watch for increases in P

8. Rotate Crops • Break the life cycles of pathogens • > 3 yrs between crops in the same family • Some pathogens cause disease among multiple plant families • Include appropriate rotational crops to increase soil organic matter

9. Exclude Pathogens • Destroy vines, etc. post-season • Removes sources of inoculum • Sterilize plant stakes between crops • Clean tools, equipment frequently • Prohibit tobacco use

10. Make Life Difficult for Pathogens • Mulches • Plastic or plant-based • Reduce splash dispersal of pathogens • Protect fruit from soilborne pathogens • Row orientation • Maximize air movement • Minimize leaf wetness periods • Irrigation management

11. Variety Selection • Use resistant or tolerant varieties wherever possible

12. Angular Leaf Spot - Cucumber • Favored by cool, wet weather • Affects foliage and fruit • Seedborne • Some cultivars advertised as resistant

14. Mildews of Cucurbits • Downy mildew • New strains appeared in 2004 • More aggressive on resistant varieties • Powdery mildew • Always appears in the Midwest in mid-summer • Defoliates and predisposes plants to other diseases • Disease resistance tables: http://vegetablemdonline.ppath.cornell.edu/Tables/TableList.htm

15. Best performers - NCSU trials 2006 (slicing cucumbers)** *Rating: 0=none; 1-2=trace; 3-4=slight; 5-6=moderate; 7-8=advanced; 9=dead plant **http://cuke.hort.ncsu.edu/cucurbit/cuke/cukemain.html

16. Use “Clean” Seeds • Sanitizing seed treatment may be needed: hot water treatment • Fact sheet: http://ohioline.osu.edu/hyg-fact/3000/pdf/3086.pdf

17. Water Bath Temperatures and Treatment Times * Cucurbit seeds may be damaged by hot water treatment

18. Seed Treatment Cautions • Use new, high quality seed • Treat a small sample first and test for germination • Treat close to time of planting (within weeks) • Treat only once • Fact sheet: http://ohioline.osu.edu/hyg-fact/3000/pdf/3086.pdf

19. Producing Healthy Transplants • Practice good sanitation in the greenhouse • Use new or sanitized plug trays or flats and pathogen-free mixes • Sanitize equipment • Install solid flooring; raise seedling trays • Limit movement of personnel and equipment between greenhouses • Clean benches, greenhouse structure thoroughly after the crop; close up greenhouse

20. Prevent Damping-off • Don’t overwater • Incorporate 10% stable compost into planting mix • Significantly reduces damping-off • Drench or incorporate biocontrol products

21. Prevention of Pythium damping-off

22. Prevention of Rhizoctonia damping-off

23. Preventing Other Diseases • Do not raise exotic or experimental vegetable varieties, or plants from saved seed, in the same greenhouse with commercial seedlings unless all seeds are treated • Avoid raising or holding ornamental plants and vegetables in the same greenhouse • Exclude insects (may carry viruses)

24. Maintain conditions in the greenhouse that do not favor disease development • Maintain relative humidity as low as possible • Good air circulation • Proper temperatures • Handle plants as little as possible

25. Field Options: Pre-plant • Biofumigation • Mustards, broccoli residue • Muscodor • Broad-spectrum activity • Biocontrols • Contans • Narrow-spectrum (Sclerotinia only)

26. Post-Planting Options • Bringing out the Band-Aids • Biological products • Chemical products • Plant extracts/oils • Compost teas

27. Disease Management Alternatives for Organic Tomatoes

28. Disease Management:Squash • Winter squash ‘Taybelle’ • Floating row covers + pyrethrum to protect plants from beetles • Foliar sprays • Armicarb • Milk • Stylet oil • Neem oil • Serenade • Compost tea • Sulfur

29. Powdery Mildew Management

30. Bacterial Wilt

31. National Organic Standards/Related Subjects • The National Organic Program • http://www.ams.usda.gov/nop/ • USDA links to organic-related material • http://www.ams.usda.gov/nop/nop2000/nop2/fedorganlinks.htm • Organic Materials Review Institute • http://www.omri.org/

32. Additional Information….. • ATTRA (Appropriate Technology Transfer for Rural Areas) • http://www.attra.org • Organic Agriculture Consortium • http://www.organicaginfo.org • NEON (Northeast Organic Network) • http://www.neon.cornell.edu/ • Anusuya Rangarajan • Department of Horticulture121 Plant Science Building Cornell University, Ithaca, NY 14853 • Phone:(607) 255-1780

33. ATTRA Sustainable Management of Soil-borne Diseases http://attra.ncat.org/attra-pub/soilborne.html • Compost Production and Use (MSU) http://www.hrt.msu.edu/course/HRT491/Compost/CombinedCompost.pdf • Composting at Home (OSU)http://ohioline.osu.edu/com-fact/0001.html • http://www.oardc.ohio-state.edu/millerlab