Botrytis Blight and Young Upper Leaves Dying on Tomatoes in Greenhouses

Preventing Botrytis

• Botrytis thrives in cool, damp places. Open greenhouse doors and sides on dry days for good circulation. Provide fans for air movement when you must close your greenhouse. Avoid watering plants with hand-held hoses and overhead sprinklers. Choose drip irrigation to water soil and keep plants dry. Poke holes in plastic mulch used along walls to allow rain to drain.

  Remove bottom leaves to help prevent mold spores from splashing onto plants. Prune, leaves and branches and plant transplants far enough apart to allow air movement. Spacing is dependent upon the variety.

Symptoms

• Botrytis affects plants very early in growth as a damping off disease. Look at tomato seedling stems at soil level. Remove seedlings with dark, moist stems.

  Look at plant leaves for water spots. Stem lesions are tan-colored, watery soft spots. Infected areas grow gray, fuzzy mold.

  Look for round, ringed spots on fruit. The skin remains intact while the inner portion becomes soft and soggy. Remove tomatoes and watch nearby plants closely for symptoms.

Management

• Apply fungicides when cool, damp weather begins, before symptoms appear, as a preventative. Botrytis becomes fungicide-intolerant easily. Avoid using fungicides after symptoms start. Remove all infected plant parts immediately. Burn, bury or throw infected material away.

  Managing upper leaves is more difficult than expendable lower leaves. Pruning upper leaves removes sunburn protection. Coat upper leaves with fungicide to help control spores that blow in with the wind. Remove upper branches. New growth begins at each node and will replace pruned branches.

Fall Clean Up

• Botrytis spores overwinter on plants and structures. Remove twine and clips used to grow tomatoes horizontally. Remove tomato cages and disinfect before storing for winter. Disinfect pruners, scissors, trowels, rakes and sprayers. Wash gloves, aprons, coveralls and cloth tool holders before storing.

  Wash all parts of the greenhouse. Spray the greenhouse cover with a hose to wash away botrytis spores. Open all doors and sides to allow airflow to dry the structure. Allow the soil surface where water landed to dry before planting the next crop.