There are a number of diseases of tomato that can cause the plants to wilt. The two diseases described here are fungal vascular wilts. The wilting is caused by fungi. The slime they produce clogs the water-transporting veins of the plant. Both fungal vascular wilts can kill the plants completely.

Verticillium wilt is caused by Verticillium albo-atrum and V. dahliae. Both Verticillium species cause nearly the same symptoms, and can infect nearly 200 species, including many flowers, trees and vegetables. Tomato, potato, pepper, eggplant, artichoke, beets, broad beans, turnip, radish, cucumber, muskmelon, and watermelon are severely affected. Asparagus, bean, broccoli, Brussels sprouts, cabbage, cauliflower, celery, chive, collards, garlic, kale, kohlrabi, leek, lettuce, mustard, onion, parsley, peas, rutabaga, spinach, and turnip are sometimes affected. Corn, grain, and grass are not hosts.

Fusarium wilt of tomato, caused by Fusarium oxysporum f. sp. lycopersici, was first described in England in 1895. It was once the most common and destructive tomato disease. Tomato is the major host; eggplant and several weeds can also be infected. There are other Fusarium fungi that cause wilts of other plants.

Symptoms. Verticillium wilt often begins with wilting during the hottest part of the day and recovering at night. The leaves may turn yellow, starting at the edges and between the veins, and spreading inward. Usually both sides of the leaf are affected. Leaflets may also show a characteristic V-shaped or fan-shaped yellowing, with the widest part of the V on the leaf edge. The narrow part is on the interior of the leaf, but not necessarily bordered by the veins. The yellowed areas will eventually turn brown and die. Generally, older leaves are affected first. Symptoms progress up the plants until only a few leaves remain on the top of the plant. Generally both sides of a plant are affected equally. Plants affected when young may be stunted. Plants often show no symptoms until they are mature and bearing heavily.

Fusarium wilt begins with lower leaves wilting or drooping, turning yellow then brown, and dying. Often just one branch or branches on one side of the plant will show symptoms. Leaflets on one side of the petiole may be affected, while those on the other side may be unaffected. Bases of affected stems are sometimes enlarged. Symptoms often become apparent while fruit is enlarging, although plants may be affected at any age, from seedling to maturity. Fruit infection is possible, but not common. When the fruit is cut open, a brownish ring can be seen around the edge of the fruit, and lines can be seen in the dividing walls.

Distinguishing between the diseases. When the stem is cut open, the ring of vascular tissue is brown, but the center of the ring will remain white. Cut the stem open lengthwise, and see how far up the plant the dark vascular discoloration extends. In verticillium wilt, it does not occur as far up the plant as it does in fusarium wilt. Discoloration does not occur in the petioles in verticillium wilt. The pith of the stem is not affected in either disease.

Symptoms may be two sided in verticillium wilt and one-sided in fusarium wilt, but this is not always true. Either disease may cause one-sided or two-sided symptoms. Verticillium wilt generally affects plants when they are nearing maturity. Fusarium wilt can affect plants at any growth stage. Generally speaking, the two diseases are very similar to one another, and must be differentiated by an experienced diagnostician.

Similar diseases. Bacterial canker also causes the plants to wilt. Entire leaves are curled down, while the edges of the leaves are curled upwards. Edges of the leaves turn brown. When the stem is cut at the base of the plant, a yellow to white ooze is seen. This disease also causes birds-eye spots on the fruit.

Prevention.

For Verticillium: Use a 3 to 4 year crop rotation. There are many potential hosts. Corn and grains are non-hosts and are recommended in the rotation. Practice strict weed control, as there are many weed hosts. If there is currently a problem with Verticillium, remove and destroy vines and roots if possible. Do not plow under debris as the fungus can survive in the soil. Control the nematode Pratylenchus penetrans, if present, as this nematode can cause an increase in symptoms.

For Fusarium: Use disease-free seed and transplants. A 5 to 7 year crop rotation may help prevent losses. Disinfest greenhouse soil; clean all tools, containers, benches, etc. Use nitrate nitrogen (such as calcium nitrate) rather than ammonium nitrogen which will cause a decrease in soil pH. Use localized fertilizer placement to feed the plants rather than the fungus. Do not flood irrigate or use pond or ditch water to irrigate.

For both fungi: Resistance is available and is very important in the control plan. There are several races of Fusarium. See current recommendations for races found in your area, and choose resistant varieties accordingly. A soil pH of 7 is best to prevent both Fusarium (favored at pH 6.5) and Verticillium (favored at pH 7.5).

References.

• Jones, J.P. 1991. Fusarium Wilt in Compendium of Tomato Diseases. APS Press. St. Paul, MN. p. 24. J.B. Jones, J.P. Jones, R.E. Stall, T.A. Zitter, eds.
• Pohronezny, K.L. 1991. Verticillium Wilt in Compendium of Tomato Diseases. APS Press. St. Paul, MN. pp 23-24. J.B. Jones, J.P. Jones, R.E. Stall, T.A. Zitter, eds.
• Sherf, A.F. and A. A. MacNab. 1986. Vegetable Disease and Their Control. John Wiley and Sons, New York.

By: Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998

Reviewed by: T. Jude Boucher, IPM, University of Connecticut. 2012

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

The information in this document is for educational purposes only.  The recommendations contained are based on the best available knowledge at the time of publication.  Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.  The University of Connecticut, Cooperative Extension System, College of Agriculture and Natural Resources is an equal opportunity program provider and employer.