My tomato plants all got early blight; will my soil be safe to use again next spring?

August 27, 2020 Ask the Expert, Managing Insect, Diseases, and Animal Pests

Question:

My tomato plants all got early blight. Wondering if my soil will be safe to use again next spring?

Answer:

It’s a very common disease of tomatoes in Maine. Here’s an excerpt from our Early Blight of Tomato fact sheet that offers some next steps: 

Survival and Dispersal

The fungus spends the winter in infected plant debris in or on the soil where it can survive at least one and perhaps several years. It can also be seed-borne. New spores are produced the following season. The spores are transported by water, wind, insects, other animals including man, and machinery. Once the initial infections have occurred, they become the most important source of new spore production and are responsible for rapid disease spread.

Control

  1. Use only clean seed saved from disease-free plants.
  2. Remove and destroy crop residue at the end of the season. Where this is not practical, plow residue into the soil to promote breakdown by soil microorganisms and to physically remove the spore source from the soil surface.
  3. Practice crop rotation to non-susceptible crops (3 years). Be sure to control volunteers and susceptible weeds.
  4. Promote good air circulation by proper spacing of plants.
  5. Orient rows in the direction of prevailing winds, avoid shaded areas, and avoid wind barriers.
  6. Irrigate early in the day to promote rapid drying of foliage.
  7. Healthy plants with adequate nutrition are less susceptible to the disease.
  8. Minimize plant injury and the spread of spores by controlling insect feeding.
  9. Hand-picking diseased foliage may slow the rate of disease spread but should not be relied on for control. Do not work in a wet garden.
  10. Use resistant or tolerant varieties.”

Mulching with shredded tree leaves or straw immediately after transplanting tomato seedlings or planting tomatoes in plastic mulch will help reduce the spread of disease spores. Irrigating the soil and not wetting the foliage will also make a big impact on disease management.