Asked July 8, 2015, 4:50 PM EDT

How to stop early blight on tomatoes We treated with mancozeb every other week. Also we used liquid 2 weeks ago now most of plants are infected.

Jefferson County Kentucky

1 Response

It sounds as if you have done all that you can. Blight disease in tomatoes is frustrating but unfortunately common, especially in such wet weather. Correct identification of fungal disease is important as one of the best controls is to remove infected plants as soon as possible to remove the source of the fungus. Applying fungicide is the last choice and spraying too often can result in fungicide resistance, over-exposure to fungicides, and plant phytotoxicity (plant tissue burning due to heat, light and chemical exposure).


As a reminder, these hints may prove helpful for growing tomatoes successfully.

Tomatoes and other plants in the solanacea family do need a little more consideration when deciding what and where to plant. (These include peppers, eggplant and potatoes.) Whether you start them from seed or purchase them as bedding plants remember:

Disease resistant varieties are best!

Tomatoes should have the letters VFFNTA. These letters represent disease and nematode resistance.

a) V – Verticillium wilt.

b) F – Fusarium wilt, FF indicate 2 most common fusarium strains.

c) N – Nematodes (microscopic plant parasite)

d) T – Tobacco mosaic virus.

e) A – Alternaria leaf spot.

Disease resistant is not disease proof so good gardening sanitation and practices are still necessary!

Indeterminate or determinate? Determinate tomatoes tend to ripen all at once, are bush like and are great for canning. Indeterminate varieties ripen off and on through the season, are vine like and the plants live a bit longer.

Rotate the crop. Do not plant them in the same place within a 3 year period. This includes any plants in the solanacea family!

Use a fertilizer labeled for tomatoes or veggies low in nitrogen but higher in potassium and phosphorus.

Better yet, get the soil tested and follow or recommendations for your particular garden plot.

Be prepared to mulch the plants for soil moisture and temperature control. Mulching also creates a layer between the soil and plants which can aid in disease control.

Be consistent with the watering.

Many other fungal diseases can cause tomato die back as well:

For your information I have included links that may help you select fungicides and general gardening in Kentucky information.

*A homeowners Guide to Fungicides:

ID 128 – Home Vegetable Gardening in KY:

Feel free to contact our office if you have other questions.

Let me know if I can help you further!

Carol Wilder
Horticulture Technician
Jefferson County Cooperative Extension Service
810 Barret Ave
Louisville KY 40204