Cucurbit Crop Bacterial Wilt
Bacterial wilt of cucurbits is often overlooked or undiagnosed in home gardens, but this disease has the potential to cause economic loss for producers growing vegetables for local markets. This disease is specific to cucurbits – a family that includes cucumbers, squash, melons and pumpkins. Bacterial wilt primarily affects cucumber and cantaloupe. Damage to other cucurbit crops is typically less severe.
Bacterial wilt is carried and transmitted by cucumber beetles as they feed on plants. These beetles feed on a wide range of host plants, and the adults can survive winters in protected areas like plant debris or fencerows. Because of their prevalence and overwintering ability, cucumber beetles are likely to be pests each year here. Once cucumber beetles feed on plants infected with the bacterial wilt organism, they carry it in their guts, potentially infecting plants they feed on in current and following season.
Bacterial wilt produces a sticky sap-like substance inside plants. This clogs the vascular system, causing plants to wilt and ultimately die. The substance is visible when plant stems are cut by pulling the knife away from the cut and looking for threads of sticky slime. Once infection has occurred, it is too late to rescue affected plants. Leaf wilt is often the first symptom noticed, followed by wilting of entire vine. Wilted leaves turn dark green, then brown as they die.
Bacterial wilt symptoms may be mistaken for squash vine borer damage, which also causes wilting and plant death. Splitting open the vines will reveal if squash vine borer is the culprit. Look for a whitish caterpillar with a brown head or frass, a saw-dust like material that is evidence of vine borer feeding.
Prevent Bacterial Wilt
Prevention of bacterial wilt in cucurbit crops depends on controlling the cucumber beetle. The first step in doing this is good sanitation – remove and destroy infected plants to prevent beetles from overwintering in debris. Because cucumber beetles also feed on flowers, sanitation of nearby flower gardens is also imported. Remove dead annual flowers, dead lower leaves of perennial flowers, fallen leaves and other debris that could provide an overwintering site for cucumber beetles.
Excluding cucumber beetles with use of row covers or screens can be an effective control in small plantings. A disadvantage of this control is that covers must be taken off before bloom to allow for pollination.
Preventive insecticide application is another option, but application must begin as soon as seedlings emerge or soon after transplant to prevent beetle feeding and disease transmission. Check UK’s Home Vegetable Gardening and Commercial Vegetable Production Guides for insecticide recommendations: UK Department of Horticulture.