The most common virus disease in Iowa is tomato spotted wilt virus (TSWV), but others can occur. TSWV causes distinctive yellow ringspots on mature fruit. Foliage also can be affected; plants are usually stunted and tip leaves show a purplish discoloration. Thrips, which are small (1 ⁄4 inch long) green-brown insects, spread the virus. Plants can be affected as transplants while growing in a greenhouse; after transplanting, stunting and failure to set fruit may be the most noticeable symptoms.
Other viruses are spread by aphids or leafhoppers and can cause leaf curling, yellow or green mosaic patterns on the leaves, “shoestringing” of leaves, or a bronzing appearance. Fruits also are affected with mosaic patterns, streaking, or mottled areas.
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