he main reason for wilting. The fungus ismost active at temperatures between 80 and 90 degrees F., seldom being a serious problem wheresoil and air temperatures remain low during most of the growing season. Control can be obtained bygrowing plants in disease-free soil, using disease-free transplants, and growing only resistantvarieties. Verticillium WiltCausal Agent(s): (fungal - Verticillium albo-atrum)The first symptom is yellowing of the older leaves, followed by a slight wilting of the tips of theshoots during the day. Older yellowed leaves gradually wither and drop, and eventually the plant isdefoliated. Verticillium wilt does not show the one-sided effect as does Fusarium wilt. Leaves fromVerticillium infected plants sometimes show brown dead spots that may be confused with thosecaused by other fungi. However, they are lighter in color and do not show concentric zones as inearly blight. In late stages of the disease, only the leaves near the tips of the branch remain alive.When the stem is cut lengthwise, the base shows a discoloration of the woody tissue similar toFusarium, but is usually darker, and generally it occurs only in the lower part of the stem. The fungusenters the plant through the feeder roots and grows into the stem in the woody conducting vesselsjust under the cortex. The fungus lives in the soil for a long time and it is exclusively the source ofinfection. Progress of the disease is favored by cooler temperatures and is retarded by the hightemperatures that are favorable to Fusarium wilt. Locating seedbeds and fields in Verticillium-freesoil, and using resistant varieties are the most effective means of controlling the disease. Gray MoldCausal Agent(s): (fungal - Botrytis cinerea)Plants become more susceptible to this disease as they become older. It is mostly a problem ingreenhouses, but it can also affect tomatoes in the field. The fungus first becomes established ondead leaves at the base of the plants. A heavy...
