Symptoms of Early Blight in tomato and potato range from damping-off, collar rot, stem canker, leaf blight, as well as fruit and tuber rot. There are foliar symptoms that include small dark flecks on older leaves which grow to become brown-black angular areas surrounded by a yellow halo. These spots have rings in them that give them a ‘target’ appearance.
As the spots spread the whole leaf may turn yellow and die. On tomato fruit the spots are usually sunken in. The lesions usually start at the point of the stem attachment and may expand to the entire upper portion of the fruit. Older lesions will sometimes be covered in black fungal spores called conidia.
Early blight is caused by the fungus Alternaria solani. Potato and tomato are the main hosts of A. solani Other Solanaceae plants including eggplants, pepper, horse nettle, cucumber and zinnia are also known hosts.
The pathogen survives on infected crop debris, and in the soil for years. It can also overwinter on volunteer hosts and weeds. The spores are spread by wind and splashing water. Infection occurs directly or through stomata on older leaf tissue and through wounds. Symptoms will appear about a week after infection.
You can control this by ensuring you have pathogen free seed and resistant transplants. Reduce sources of disease such as weeds and plowing under crop debris. Rotate to non-hosts for at least two years. Avoid standing water in your garden since the fungus thrives in hot wet environments. You can also apply fungicides every 7-10 days.
For more information, call the AgriLife office at 498-4071 in Odessa or at 686-4700 in Midland, email jeanette.castanon@ag.tamu.edu or visit aggie-horticulture.tamu.edu or westtexasgardening.org.
July 12, 2020 at 12:45PM
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GARDENING: Early blight in potatoes and tomatoes - Odessa American
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