Answer: Some bacterial wilt is spread by insects and they spread the bacteria from plant to plant as they feed. To test for bacteria, cut a wilted stem near the base of the plant and squeeze out the sap--look for a milky white substance. Touch the tip of a knife to the ooze, and if as you withdraw the knife it strings out in a fine thread, you have a bacterial infection. There is no chemical control for this type of wilt; the best bet is to control the beetles--or better yet, grow resistant varieties.
There are other fungal diseases which could be the culprit, such as fusarium wilt and verticillium wilt. These diseases are most common when the same crops are grown in the same place year after year. They cause the leaves to turn yellow, then brown, then die. Lower leaves are affected first. The fungus overwinters in the soil, so cleaning up crops residue at season's end can help. The best solution is to rotate your crops and plant resistant varieties.
It is disappointing to lose your entire veggie garden to such a problem. Once course of action you can take is to turn the former veggie garden into a flower garden for a few years and raise your tomatoes and peppers in containers on a sunny deck or porch.
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