Basics of Managing Diseases in the Vegetable Garden

1. Basics of Managing Diseases in the Vegetable Garden Kenny Seebold Plant Pathology Department

2. Management Basics • Location – pick areas that are: • well-drained (soil) • open and sunny • away from commercial fields (vegetables or tobacco) • Practice crop rotation • Rotate away from vegetable crop for 2-3 years with unrelated crops • Keeps pathogens from building up in soil by depriving them of food • Grasses, corn (including sweet corn) are good choices

3. Groups of Related Crops Group D beans (snap, lima, pole) English peas snow peas southern peas Group B cabbage cauliflower broccoli Brussels sprouts mustard turnips collards kale Group C pepper (all) tomato eggplant irish potato Group A watermelon cucumber squash cantaloupe pumpkins gourds Group E beets Swiss chard spinach Group G sweet corn Group F onions shallots garlic leeks

4. Rotation Options - Tomato

5. Rotation Options - Cucurbits

6. Management Basics • Using manures and composts • Improves soil condition and possibly ‘health’ • Incorporate at least 4-6 weeks before planting • Allows organic matter to break down and not serve as food for pathogens • Don‘t compost diseased plants Compost Green manure (rye/hairy vetch)

7. Management Basics • Soil condition and fertility are critical issues • Test soils before planting • Soil pH can influence some diseases – particularly on potato and sweetpotato • Determines nutrient status and pH • Add nutrients as dictated by soil test • Don’t over-feed during the season • Try to achieve vigorous, but not rank, growth • Too much or too little fertilizer can promote certain diseases

8. Management Basics • Plant resistant varieties • Effective and inexpensive form of disease management • Can reduce fungicide use as well • Resistance doesn’t mean “immunity” • Resistance ‘package’ will vary by crop • Information listed in most seed catalogs or on seed packets RESISTANCE CODES FOR TOMATOES A=Alternaria (ASC) F=Fusarium wilt L=Septoria leaf spot N=nematode S=Stemphylium (St) TMV=tobacco mosaic virus TSW=tomato spotted wilt V=Verticillium wilt

9. Management Basics • Sanitation (keep pathogens out) • Pathogen-free seed & transplants • Inspect store-bought plants, reject those with diseases • Buy commercially produced seed if possible • Follow proper extraction and treatment procedures for saved seed • Select from healthy, non-hybrid plants • Plow under / remove old crop quickly after harvest • Clean tools, etc. (between uses, and those that have been used in other gardens)

10. Hot Water Treatment of Seed • Can be used with many vegetables (see ID-36) • Not safe for legumes or cucurbits other than cucumber • Will inactivate most pathogens except those that have become associated with the embryo • Temperature and soaking time depends on crop • Critical factors -> poor efficacy or crop damage can occur… • Invest in a quality thermometer • Must agitate water to maintain uniform temperature • Use weighted mesh bag to hold seed • Dip in cold water to cool quickly • Dry completely before storage / planting Images – S.A. Miller, Ohio State U.

11. Recommended Temperatures and Soaking Times for Hot-Water Disinfection of Selected Vegetable Seeds

12. Chemical Seed Soaks • Bleach • Use 1 qt commercial-grade bleach to 3-4 qt of water • Add 1-2 drops of dish detergent to decrease surface tension • Use ~1 gallon of solution per lb. of seed -> soak time is 1 minute • Rinse thoroughly afterward; spread to dry • Trisodium phosphate (TSP) • Concentration of solution = 10% (1 part TSP, 9 parts water) • Use ~1 gallon of solution per lb. of seed -> soak time is 15 minutes • Rinse thoroughly afterward; spread to dry

13. Management Basics • Plant at the right time • Early planting = cool soils • May see problems with root rots & damping-off (beans, corn, cucurbits) • Plant when soil temperatures are above 60F at 2-inch depth • Late planting = warm temperatures • Can see more problems with bacterial and viral diseases • Reason: warmer temperatures and higher insect populations

14. Management Basics • Watch that garden hose! • Try not to saturate soils • Use drip irrigation to keep foliage dry • Can use drip tape or soaker hoses • Can water individual plants at their bases • Water early vs. late in the day if irrigating overhead • Allows leaves to dry quickly

15. Management Basics • Control weeds in and around the garden • Improves air movement • Removes potential sources of pathogens and insects • Spread things out • Use wider rows, proper ‘in-row’ spacing • High plant populations can equal more disease • Reason: poor air movement & increased plant-to-plant spread

16. Management Basics • Don’t work in the garden while leaves are wet • Avoid handling plants, stringing, harvesting at this time • Can spread disease easily at this stage • Use mulches where practical • Plastic mulches, straw/hay • Creates a physical barrier between soil and plants • Reduces soil splash and pathogen spread

17. Southern Blight of Tomato barrier

18. Management Basics • Remove diseased plants (rogueing) • Prevents further plant-to-plant spread • Not practical if disease exceeds 5-10% of planting or on very large operations • Mostly used on virus diseases and some fungal diseases (stem rots)

19. aphids Management Basics • Control insects • Insects can carry and transmit fungi, bacteria, and viruses • Bacterial wilt of cucurbits • Stewart’s wilt of corn

20. Management Basics • Fungicides and bactericides • Needed for vegetable crops in KY in most years • Proper application is important for good results • Preventive use is best • Check plants regularly for diseases and pests • Begin treatments when conditions favor disease, continue as needed • Ideally want to begin before symptoms are seen • At the latest, treat when symptoms first appear • Follow a schedule based on weather and crop • Dry weather = longer time between sprays (10-14 days) • Wet weather = shorter time between sprays (5-7 days)

21. Management Basics • Other considerations for applying fungicides • Make sure that the product can be used on the crop to be sprayed!!! • Use the correct rate • Invest in good-quality measuring spoons, cups, and containers • Mix carefully • Make sure you have calibrated your sprayer • Assures that the proper dosage will be applied • Too little product = poor control, wastes time and product • Too much product = violates label, wastes product and money, could cause injury • Apply fungicides carefully • Protect yourself with gloves, safety classes, clothing • Aim to get the best coverage of foliage possible