Late Blight on Tomatoes
Many folks are experiencing Late Blight on their Tomatoes or Potatoes in their gardens this time of year. The plant disease can occur on other vegetables as well.
Late Blight is caused by a fungus called Phytophtora infestans, a water mold that grows on wet leaves. Millions of spores spread the disease in wet weather conditions. Spores can travel long distances by air and can be washed through the soil and infect potato tubers.
For a little history, Late Blight was the cause of the 1850’s Irish potato famine during which million of people starved and were forced to emigrate. Not something you want in your garden.
The fungus can survive from season to season. Infected plants from last year, seed potatoes and tomato transplants can all spread the disease.
If you have Late Blight you either destroy the plant or control the disease with a fungicide.
There are only a few homeowner or residential labels for fungicides that control Late Blight. Commercial grower products are higher active ingredients of the named products below.
Chlorothalonil and Mancozeb are the common fungicides used as a protectant and they are not systemic. Copper is labeled for the disease but it’s not very effective.
Liquid Ornamental & Vegetable Fungicide is a 12.5% Clorothalonil and is labeled for home gardeners.
The recommended rate is 2-4 Tablespoons per gallon.
Dithane M-45 is an 80% mancozeb product and the rate is 1.5 Tablespoon per gallon.
For commercial use there are various formulations of Chlorothalonil such as Bravo and a product called Chlorosel Pro 720, a 50% Chlorothalonil.
Organic gardeners can only use copper and it isn’t very effective. There may be some natural fungicides but they would not be labeled for specific use on blights.
Fungicides can be obtained through website or call 1-800-373-5008
