The Q&A Archives: Wilting and blackening leaves on peppers

Question: My beautifully thriving container-grown peppers just started to wilt and drop their leaves. I notice the leaves that are dropping have a "spray" of black on them. I suspect a fungus, since St. Louis has had very hot and humid weather. I am trying to strip off all the affected leaves. Is there something else I can do to save these plants?

Answer: I can't give you a positive identification on the disease, but it sounds like gray leaf spot. The symptoms of this disease include irregularly-shaped pale grayish-brown spots that appear first on lower leaves and gradually work their way up the plant. Often, the centers of the spots decay to a point where the leaf actually has tiny holes in it. The disease is most common in warm, humid climates.

The disease-causing fungus, Stemphylium solani, overwinters on dead plant tissue, so clean up the plants at the end of the season and compost them, rather than tilling them under. If you use stakes or cages, clean all plant material off these; otherwise you'll be introducing disease spores next spring.

If you notice the leaf spots next year, pick the affected leaves off immediately, and keep leaves as dry as possible. Don't use an overhead sprinkler to water the plants; rather, water the soil directly. I have had some luck using a neem-based fungicide (available from Gardener's Supply; 1-800-863-1700, web site: on these types of leaf diseases.

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