Vegetable Disease Update for 2011

1. Vegetable Disease Updatefor 2011 Kenny Seebold Extension Plant Pathologist

2. Topics • Fungal Leaf Blights of Kentucky Vegetables • Early blight and Septoria blight of tomato • Leaf mold of tomato • Powdery mildew of cucurbits • Attack of the Exploding Watermelons • New Vegetable Fungicides for 2012

3. Early Blight and SeptoriaLeaf Spot of Tomato • Most common fungal diseases of KY tomatoes • Most aggressive during wet weather with mild-to-warm temperatures • More common in the field than in greenhouses or high tunnels

4. Early BlightFoliar symptoms late stage early stage

5. Early BlightFruit symptoms

6. Septoria Leaf Spot

7. Early Blight and Septoria Leaf SpotDevelopment and Spread • Early blight: Alternariasolani • Septoria Leaf Spot: Septorialycopersici • Pathogens survive in soil, crop debris, weeds, and seeds (early blight) • Spread by wind, rain splash, and mechanical means • Plants are most susceptible after fruit set • Long periods of leaf wetness needed for infection • Ideal temperature range is between 70 and 85F • Nitrogen deficiency increases susceptibility to early blight

8. Early Blight and Septoria Leaf SpotManagement • Sanitation and crop rotation • Remove debris promptly • Gardeners can remove older leaves or symptomatic foliage • Utilize drip irrigation • Water earlier in the day if irrigating overhead • Maintain N at recommended levels • Avoid narrow row spacing and high plant populations • Use disease-free planting material • Resistant / tolerant varieties (early blight) • Fungicides

9. Early-Blight Resistant Varieties • Slicers • Defiant • Legend F1 • Mountain Fresh Plus • Mountain Supreme • JTO-99197 F1 • Plum/cherry/grape types • Mountain Magic • Plum Dandy

10. Fungicides for Tomato Fungal Blights • Recommended materials: • ORGANIC Producers: • Fixed copper (OMRI-approved) such as Nordox, Badge X2, Ortho Elementals Copper • CONVENTIONAL Producers:

11. Leaf Mold of Tomato • Increasingly common problem • Most aggressive during overcast and humid weather • More common in greenhouses and high tunnels than in the field

12. Leaf MoldFoliar symptoms upper leaf surface

13. Leaf MoldFoliar symptoms upper leaf surface

14. Leaf MoldFoliar symptoms

15. Leaf MoldDevelopment and Spread • Caused byFulviafulva • Pathogen survives in soil and crop debris, also seed • Spores can survive at least 1 year • Organism also produces sclerotia that can survive in soil for long periods • Spread by wind, rain splash, and mechanical means • Oldest leaves are most susceptible • High humidity required for spore germination and infection • Infection is greatest when daytime RH exceeds 85% and reaches 100% at night

16. Leaf MoldManagement • Sanitation • Hand-remove symptomatic leaves at disease onset • Remove and destroy tomato debris immediately after crop cycle • Clean greenhouse surfaces with 10% bleach or peroxide • Can also steam greenhouse or close up and allow inside temperature to exceed 120F for several days • Manage temperatures and humidity • Vent structure and use fans to move air • Flush humid air when cool nights are expected • Keep night temperatures above 65F • Avoid wetting foliage • Use disease-free planting material • Resistant varieties are available, but pathogen mutates quickly • Fungicides – useful, but environmental control is more important

17. Fungicides for Tomato Leaf Mold • ORGANIC Producers: • Fixed copper (OMRI-approved) such as Nordox, Badge X2, Ortho Elementals Copper • CONVENTIONAL Producers: Quadris cannot be used in the greenhouse Quadris Top cannot be used for transplant production

18. Powdery Mildew of Cucurbits

19. Powdery MildewFoliar Symptoms

20. Powdery MildewDevelopment and Spread • Pathogen (Podosphaeraxanthii) is an “obligate” – needs living tissue to survive • Can overwinter on crop residue (foliage) • Pathogen is windborne • Favored by high RH and moderate temperatures • Development of disease is rapid under favorable conditions • PM development is slowed at temps above 95 ⁰F • Tends to become severe after fruit set • Generally worse in late summer & early fall in KY

21. Powdery MildewManagement • Plant in areas with good air drainage & little shade • Resistant varieties • Effective • May reduce or even eliminate the need for fungicides

22. Resistant VarietiesPowdery Mildew • Summer Squash • Lioness (SN) • Prelude II (CN) • Zucchini • Wildcat • Acorn Squash • Tay Belle PM • Cucumber • Speedway (slicer) • Indy (slicer) • Cobra (slicer) • Calypso (pickling) • Muskmelons / Cantaloupes • Athena • Aphrodite • Minerva • Pumpkin • Camaro • Gladiator • Magic Lantern • Warlock From ID-36

23. Powdery Mildew Fungicides • Recommended materials: • ORGANIC Producers: • Fixed copper (OMRI-approved) such as Nordox, Badge X2, Ortho Elementals Copper • Sulfur: 2-35 lb/A (depending on formulation) • CONVENTIONAL Producers: *Pumpkins, winter squash, melons only

24. Bacterial Fruit Blotch of Watermelon

25. Allen County, July 2011

26. Allen County, July 2011 The first case of bacterial fruit blotch in KY was confirmed

27. Bacterial Fruit Blotch • Caused by Acidovoraxavenae subsp. citrulli • Has caused devastating losses around the world and in the U.S. • IN, southeastern states • Not found in KY before 2011 • Exclusively seedborne • Can also overwinter in volunteers • Spreads quickly in transplant houses • Infected seedlings introduce pathogen to fields • Spreads by insects and rain splash in the field

28. Bacterial Fruit Blotch • Why was the disease not seen before 2011? • Weather? • More watermelons grown now than ever before • 2011 was the worst outbreak of this disease EVER • Management • Assume that seed could be contaminated • Treat seedlings in greenhouses routinely with fixed copper • Test for BFB if disease is suspected; don’t use plants from infested houses • There are no resistant varieties • Treat in the field with fixed copper starting before flowering and continue through fruit set • Once rinds harden, infection is unlikely • The disease can be spread easily on equipment or clothing – sanitation is a must • Don’t work in wet fields • If disease is found, work in those fields last • Rotate and make sure volunteers are destroyed

29. NEW Fungicides for 2012

30. Maneb Update • Maneb fungicides are no longer available: • Registrations cancelled in late 2008. • Important fungicide and tank-mix partner with fixed copper for bacterial disease control. • Biggest impact of loss was on “maneb-only” crops like brassicas, peppers, pumpkins, and winter squash; other maneb crops could use mancozeb as a replacement. • As of March, 2011 • Manzate ProStick: can be used in place of maneb on broccoli, cabbage, lettuce, pepper, pumpkin, and winter squash. • Dithane: can be used in place of maneb on pumpkins and winter squash.

31. Quadris TopSyngenta • Fungicide • Broad spectrum • Azoxystrobin + difenoconazole • FRAC Groups 11 and 3 • 2.72 lb/A suspension concentrate • 8 to 14 floz/A use rate • Field and greenhouse* use • REI • 12 hours • PHI • 0 to 14 days (crop-dependent) • Brassicas • Bulb vegetables • Carrots • Cucurbits • Fruiting vegetables • Potatoes

32. Inspire SuperSyngenta • Fungicide • Broad spectrum • Difenoconazole + cyprodinil • FRAC Groups 3 and 9 • 2.82 lb/A suspension concentrate • 16 to 20 floz/A use rate • Field and greenhouse* use • REI • 12 hours • PHI • 0 to 14 days (crop-dependent) • Brassicas • Bulb vegetables • Cucurbits • Fruiting vegetables

33. Questions?