Preventing Anthracnose in Peppers and Tomatoes

Hot rainy weather and fields with a history of anthracnose mean high risk for for this disease in peppers and tomatoes.  Anthracnose, caused by species of the plant pathogenic fungus Colletotrichum,  causes no obvious leaf lesions on tomato foliage and only occasionally on pepper foliage under high disease pressure.  However, pepper and tomato fruits are very susceptible to the disease.  The fungus can be introduced on seeds, and survives over the winter in temperate climates associated with crop debris.  Fruits are infected when green; pepper fruits develop large lesions with salmon-colored spores when green or ripe, but tomato fruits do not develop the typical sunken lesions until they begin to ripen.  Spores of the fungus are moved about by splashing rain, so rainstorms can promote disease spread throughout a field.  Mechanically harvested processing tomatoes are particularly prone to anthracnose problems since fruits ripen at different rates but are harvested all at once.  Management practices include thorough scouting, sanitation/removal of diseased fruits, and fungicide applications.  There are some differences in susceptibility of pepper and tomato varieties to anthracnose, but none are highly resistant.

It is time now to start protecting plants from anthracnose – fungicides must be applied as soon as fruits begin to set, and continued on a weekly schedule as fruits develop.  Fungicides  labeled for use against anthracnose in fruiting vegetables (eggplant, pepper, tomato) are listed in the Midwest Vegetable Production Guide for Commercial Growers.  Several studies have shown the best results with Aprovia Top, Quadris, Quadris Top, Cabrio or Priaxor alternated with chlorothalanil or mancozeb.  Some labels may recommend a spreader-sticker; be sure to read and follow label instructions.