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Carolina Farm Stewardship Association 2012 Sustainable Agriculture Conference Sustainable and Organic Approaches To ManagingCucurbit and Tomato Diseases Anthony (Tony) Keinath Vegetable Pathologist Clemson University Coastal REC Charleston, SC
Today’s Outline Intro to Tomato and Cucurbit Diseases Important Pathogens Risks to Other Crops 5 General Control Strategies Avoidance Eradication Recommendations for Specific Diseases “More of what works, less of what doesn’t”
Avoid extremes“You can’t grow organic vegetables in the Southeast.”“All diseases can be managed organically.”
Symptoms of Important CucurbitDiseases Disease Leaves Crown Vine Fruit Downy mildew √ Powdery mildew √ Phytophthora crown √ √ √ √ and fruit rot Gummy stem blight √ √ (√) √ and black rot Anthracnose √ √ √
Spread and Survival of ImportantCucurbit Pathogens Spread Rain Survive Disease Organism Wind Splash Water in Soil Downy mildew Water Mold ** (*) -- -- Powdery mildew Fungus ** -- -- -- Phytophthora Water Mold crown and fruit -- * ** ** rot Gummy stem blight and black Fungus * ** -- * rot Anthracnose Fungus (*) ** -- *
Diseases that Affect BothCucurbit and Tomato Crops Phytophthora Southern blight crown and fruit rot Tomato, pepper, Pepper, tomato, eggplant eggplant Snap bean Snap and lima Jerusalem artichoke beans Peanut Root knot Many broad-leaved crops
5 General Control Strategies Avoidance Protection Resistance Eradication Exclusion
Challenges with Spraying for OrganicDisease Control (Protection) Favorable environment Biopesticides usually less effective than conventional fungicides Powdery mildew is exception NOP allows S and Cu only as a last resort Protectants only Labels of biopesticides are inaccurate
What is AVOIDANCE? Preventing contact between pathogen and host to prevent disease. Modifying the environment to make it less favorable for disease. One of 2 main strategies for organic disease control. Warning: pathogen is still present!
Avoidance Techniques Change planting date Raise beds to prevent damping-off Avoid wetting leaves when watering Mulch to prevent fruit rots
Eradication: Length of CropRotationsFoliar pathogens Soilborne pathogens No long-term survival Various survival structures structures Until infested debris is Sclerotia gone Oospores ≤ 1 yr for bacteria Dormant mycelia 1-3 yr for fungi and Cannot eradicate with water molds rotation Can reduce populations (= primary inoculum)
2 Crop Rotation and PlantingSchemes for Small Acreages For foliar diseases: For root and wilt Spread crops in diseases: same botanical Group crops in family far apart same botanical Slows pathogen family together spread Rotate away for 3-4 Disadvantage: Makes years crop rotation difficult Disadvantage: May increase foliar diseases in wet years
Foliar Soilborne pathogens pathogensSeparate or Group Related Tomato Solanaceous Squash Arugula Cucurbits EggplantCrops? & Broccoli Cukes Pepper Brassicas
Soil Solarization Sterilizing soil by using heat from the sun trapped under clear plastic by the “greenhouse effect” Solarize Solarizing soil potting is PARTIALLY soil in effective clear plastic bags 2 wk 8 Use 2 weeks layers in plastic June- July
Composting to EliminatePathogens Eradication of Nematodes Fungi Seeds pathogens in plant 180 debris 160 D To be safe: e 140 Peak temperatures g 120 147-158 F. for 21 r 100 days e 80 e Difficult to achieve s 60 in 1-cu-ft pile 40 Survived: F 20 Fusarium wilt of tomato 0
General Cultural Practices to AvoidDisease on All Crops Reduce leaf wetness •Drip irrigation •Increase row/plant spacing •Avoid edges of woods •Row orientation Improve soil drainage • Raised beds • Add organic matter • Compost • Cover crops
Controlling Vegetable Diseases-General Organic Techniques Bacteria Fungi (true) Reduce leaf wetness Copper does not work One- to two-year Sulfur is better option rotation Water molds Copper (oomycetes) Root diseases and Copper nematodes Potassium phosphite Improve soil drainage Not organic certified Increase organic matter Resistance
General Cultural Practices toManage Tomato Diseases Grafting •Root knot •Southern blight •Fusarium wilt •Bacterial wilt •(awaytogarden.com) High Tunnels • Prevent fruit cracking • Reduce foliar disease • Extend season • (hightunnel.org, Kansas State)
Resistant Tomato VarietiesResistance Available No Resistance Spotted wilt Bacterial spot Early blight Bacterial wilt Root knot Southern blight Late blight ‘Mountain Magic’ (campari type) Resistance in All ‘Plum Regal’ Hybrids Gray leaf spot Fusarium wilt Except grapes
Gray Leaf Spot ‘Cherokee Purple’ is v. susceptible 2-3 year rotation Avoid planting tomato and pepper next to each other Early planting Disease is favored by high temp and humidity
Controlling Cucurbit DownyMildew Copper sprays • On crops other than cucumber Avoidance • Early planting date Resistance • C. maxima • Cucumber cultivars • Tolerant • ‘Aladdin’ pumpkin • Some summer squash cv.
Controlling Cucurbit PowderyMildew Biopesticides—spray top and bottom of leaves • Organocide (fish oil + sesame oil) • Potassium bicarbonate • JMS Stylet Oil or horticultural oil Sulfur • Do not apply at 90ºF Resistant summer and winter squash and pumpkin cultivars from Harris Seeds
Survival of the GSB Fungus in Cantaloupe Crowns Nov 05 May 06 Nov 06 May 07 Nov 07 100 % Crowns with viable D. bryoniae Soil surface% Crowns with viable D. bryoniae 90 Plastic mulch 100 Soil surface 80 Buried 5 in. 90 Plastic mulch 80 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 Weeks after burial Weeks after burial
Controlling Gummy Stem Blightand Anthracnose Rotate for 3 years • Summer squash in 2nd or 3rd year Plant early Disease-free transplants Do not reuse plastic mulch Disk fields to bury debris as soon as possible after harvest
Managing Fusarium Wilt ofWatermelon Resistant cultivars Only resist. to race 1 Grafting onto bottlegourd or hybrid squash Both are susceptible to root knot Crop rotation to Hairy vetch as winter reduce build-up of cover crop/green pathogen manure Works best before soil is infested
Managing Bacterial FruitBlotch See conventional guidelines Only exception is avoid use of Actigard
Managing Cucurbit VirusesSpread by Aphids Resistant cultivars Check if conventional or GM Horticultural oil sprays Every other day Prevent infection Camouflage Rye grass between rows Kaolin clay sprays
Sustainable DiseaseManagement Organic soil Cultural management practices Check plants • Cover crops • Exclude, weekly for • Crop rotation • Eliminate and problems • Compost • Avoid disease Identify diseases to Apply select the best biopesticides control method preventatively •Bacterium or fungus? •Water mold or true fungus?