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.
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.
wilt. Photo courtesy of the Ohio State University Extension
plants affected by bacterial wilt.
Photo courtesy of R. A. Casagrande.
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.
cucumber beetles. Photo courtesy of the Ohio State University
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.
the Ohio State University, 2000