Symptoms

• On cucumber and melon, generally a distinct flagging of lateral and individual leaves occurs. Affected leaves turn a dull green.
• Sometimes wilting occurs on leaves that have been injured by cucumber beetles' feeding, but in many cases obvious feeding is not apparent.
• Leaves adjacent to the wilting leaves will also wilt, and eventually the entire lateral is affected. The wilt progresses as the bacteria move from the point of entry through the vascular system toward the main stem of the plant.

• Eventually the entire plant wilts and dies. If you cut through the stem of an affected plant and squeeze both cut ends, a white, sticky exudate will often ooze from the water-conducting tissue of the stem.
• This exudate is composed of bacterial material that plugs the vascular system of the plant. Affected stems do not appear significantly discolored.
• Bacterial wilt is closely associated with either the striped or the spotted cucumber beetle. The bacteria overwinter in the bodies of adult cucumber beetles.
• The beetles carry the bacteria when they emerge in the spring. The bacteria are spread either through the feces of the beetle or from contaminated mouthparts.
• When the beetles feed on young leaves or cotyledons, they open entry points for the pathogen.
• Once inside the plant, the bacteria travel quickly through the vascular system, causing blockages that in turn result in wilting of the leaves.
• The disease progresses from plant to plant when a carrier beetle moves through the field or when clean beetles pick up the bacteria from a diseased plant and fly to healthy plants. Larvae are not known to carry the wilt organism.

Management

• In general, more bacterial wilt is seen on the edges of fields where beetles first encounter plants. Larger plantings must be protected by insecticides.
• Carbaryl, Malathion, or rotenone insecticides or combination products are registered to treat cucumber beetles.
• They will provide control of the beetles if applied when beetles first appear in the spring.
• Early control, beginning as soon as the plants emerge, is most important as a single beetle can introduce the bacteria. One to four generations of the beetle may occur on unprotected plants and applications of these insecticides at weekly intervals may become necessary.
• Apply a light even coating of the insecticide over the entire plant, especially where the stem emerges from the soil (where the beetles often congregate).