vegetable disease - Knowledgebase Question

novi, Mi
Question by pushpamv
August 5, 2010
tomato plant has yellow black leaves. beans ,basil,okra leaves has a tainted whitish look. what organic or natural spray can i use?


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Answer from NGA
August 5, 2010

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The whitish coloration on your plants sounds like it could be powdery mildew. Powdery mildew fungi spread quickest when the humidity is high and temperatures are between 50F and 90F. To discourage the disease, plant on sites with good air drainage, give the plants plenty of space, water during the morning only, and allow the soil to dry out between waterings. Remove any affected leaves, and if your plant is heavily covered with powdery mildew you should probably remove the entire plant so the infection doesn't spread. For heavy infestations of powdery mildew, sulfur or copper sprays can be applied weekly, starting in June in your area. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step) Chemicals are most effective when combined with cultural controls.

I can't really diagnose the problem on your tomato plant; several diseases can cause the black splotches on leaves. There's a website hosted by Cornell University with a diagnostic key that you might find helpful. Just match the symptoms you see with the pictures on the site. Hope you find it helpful.
http://vegetablemdonline.ppath...

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