Vegetables, Berries, and Grapes: Spider Mites

Problem
Leaves are stippled, yellowing, and dirty. Leaves may dry out and drop. There may be webbing over flower buds, between leaves, or on the lower surfaces of the leaves. To determine if the plant is infested with mites, hold a sheet of white paper underneath an affected leaf or stem and tap the leaf or stem sharply. Minute green, red, or yellow specks the size of pepper grains will drop to the paper and begin to crawl around. The pests are easily seen against the white background.

Analysis
Mites, related to spiders, are major pests of many garden and greenhouse plants. They cause damage by sucking sap from the undersides of the leaves. As a result of feeding, the green leaf pigment disappears, producing the stippled appearance. Although mites do not attack the fruit directly, they do cause leaf drop, which weakens the plant and reduces fruit yield. If the plants are severely infected, flowers do not form or do not bloom, resulting in no fruit. Mites are active throughout the growing season, but are favored by dry weather with temperatures of 70°F and up. By midsummer (or as early as March in Florida), they may build up to tremendous numbers.

Solution
Treat infested plants with an insecticidal soap, diazinon or malathion at the first sign of damage. Repeat at weekly intervals until no further damage occurs. Make sure that your vegetable or berry is listed on the label. Hose plants frequently with a strong stream of water to wash off mites and webs.