After vine crops begin to run, gardeners and farmers often notice individual leaves with severe wilt symptoms on sunny days. Within a week or two the condition spreads to entire vines which do not recover from the wilt. This disease, called bacterial wilt, is especially common in cantaloupes and cucumbers. Squash and pumpkins may not wilt as rapidly, but may be dwarfed with extensive blossoming and branching. Watermelons are rarely affected.

Symptoms:

Wilting of individual leaves or vines of the plant is the characteristic symptom; one or more leaves wilt and become dull green. The disease spreads from the leaves downward into the petioles and then into the stem until the entire plant wilts and dies. Vine borers or soil-borne fungal pathogens may also cause cucurbits to wilt--a helpful test in diagnosis of bacterial wilt is to cut off an affected stem near the ground; if the sap is milky in appearance or sticky and stringy, the wilting is likely to be a result of bacterial wilt.

Cucumber plants affected by bacterial wilt. Photo courtesy of R. A. Casagrande.

Causal Organism:

The bacterium which causes this disease, Erwinia tracheiphila, overwinters in the bodies of the striped and 12-spotted cucumber beetles. In the spring, the beetles emerge from the ground and feed on young plants, introducing bacteria into the leaves or stems. The bacteria reproduce in the water-conducting vessels, producing gums which interfere with water transport. The beetles and bacteria are so intimately related that controlling the beetles will control infection by the bacteria. Once infection has occurred, however, no control is possible and wilting plants should be removed, if practical. The disease is not seed-borne.

Mangement:

Management of this disease is only possible through preventing the feeding of cucumber beetles on susceptible hosts. See GreenShare Factsheet on cucumber beetles for more information.

Adapted from the Ohio State University, 2000