Bacterial Wilt of Cucurbits

Bacterial wilt is caused by Erwinia tracheiphila, a bacterium that lives almost entirely inside its vector: the striped and spotted cucumber beetles (Acalymma vittatum and Diabrotica undecimpunctata). Unlike many cucurbit diseases, wet soils and high humidity are not the primary drivers. The disease spreads when infected beetles feed on susceptible plants, depositing bacteria in feeding wounds. Those bacteria colonize the xylem tissue and physically block water transport, which is why wilting appears so rapidly even in otherwise healthy-looking plants.

The timeline is unforgiving. A single infected runner may collapse within days, and whole-plant death typically follows within one to two weeks of the first visible wilt. Cutting a wilted stem near the soil line and slowly pulling the two cut ends apart will reveal stringy, sticky bacterial ooze between them, a field diagnostic that is reasonably reliable.

Because there is no curative treatment once infection occurs, the entire management strategy collapses into a single goal: keep cucumber beetles off plants during the critical early season. Floating row covers applied at transplant and held in place until the first female flowers appear are the most reliable low-input approach. Once covers come off for pollination, beetle populations should already be suppressed through whatever combination of trap crops, kaolin clay, or insecticide applications fits the operation. Roguing infected plants at first symptom limits the inoculum available to feeding beetles, slowing spread through a planting. Some cucumber selections, notably County Fair, carry meaningful resistance and are worth considering in areas with chronic pressure.