Tomato hornworms are large (2 to 3 inch long when fully grown), green caterpillars with white stripes on the body. A horn protrudes from the top rear end of the worm. Tomato hornworms feed on the leaves and fruit. Several worms on one plant can quickly defoliate it and ruin developing fruit. Because their green coloring so closely resembles tomato foliage and stems, they are difficult to see. Handpick in cooler parts of the day or use suggested biological insecticides. If you see hornworms with small, white cocoons protruding, leave them alone. These structures are the pupae of parasitic insects that help control the hornworm population and the individual wearing them is already doomed.
Verticillium and fusarium wilts are soilborne diseases that cause yellowing of the leaves, wilting and premature death of plants. These diseases persist in gardens where susceptible plants are grown. Once they build up, the only practical control is the use of resistant (VF) varieties.
Early blight is characterized by dead brown spots that usually start on the lower leaves and spread up the plant. Upon close inspection, you can see concentric rings within the spots. Although early blight is most severe on the leaves, it sometimes occurs on the stems and can cause severe defoliation. Certain varieties (Roma and Supersonic) are more tolerant of early blight than others.
Septoria leafspot is characterized by numerous small black spots on the leaves. The centers of these spots later turn white and tiny black dots appear in the white centers. The disease starts on the bottom leaves and may become severe in wet weather.
Blossom-end rot is a dry, leathery brown rot of the blossom end of the fruit that is common in some seasons on tomatoes. It is caused by the combination of a localized calcium deficiency in the developing fruit and wide fluctuations of soil moisture. The problem is especially bad in hot weather. Soil applications of calcium seldom help, though foliar calcium sprays may minimize the occurrence of the problem. Make sure the formulation is designed for foliar application or severe damage could result. Pruning causes stress to the plants that may increase the incidence of blossom-end rot. Some tomato varieties are much more susceptible to this condition than others. Mulching and uniform watering help to prevent blossom-end rot. Once the blackened ends appear, affected fruits cannot be saved. They are best removed and destroyed so that healthy fruit setting later can develop more quickly.
Poor color and sunscald occur when high temperatures retard the development of full red color in tomatoes exposed directly to the hot sun. Sunscald occurs as a large, whitish area on the fruit during hot, dry weather. It becomes a problem when foliage has been lost through other diseases such as early blight or on early varieties that normally have poor foliage cover as the fruit ripens.
