Bacterial Wilt

Bacterial Wilt

Pseudomonas, Erwinia species

Bacterial Wilt is primarily a disease of the Cucurbits, particularly cucumbers and melons, though it can also attack the Solanum crops (tomato, pepper, potato, eggplant) and corn. It is commonly transmitted by Cucumber Beetles (they transport the bacteria and create wounds for it to enter the plant). Once inside the plant the bacteria multiply and inhibit the transportation of water and nutrients. The first sign of this disease is when one or two leaves wilt in the afternoon, but then recover in the evening. This wilting eventually spreads to the whole plant and the leaves start to die off, usually without turning yellow first.

Keeping Cucumber Beetles under control can help reduce problems with this disease. You might also grow your plants under row covers. Some squash varieties are less vulnerable than others (Table Queen Acorn, Butternut, Buttercup). Removing potentially infected crop debris and rotating crops will help to reduce the source of infection. Of course you should remove infected plants immediately (and wash your hands with soap and water afterwards). If you suspect Bacterial Wilt, cut a stem near the crown and pull it apart. If the sap is stringy and viscous it is probably wilt.

To test for Bacterial Wilt in cucumber cut a stem near the ground and squeeze until the sticky sap oozes out. Leave this to dry for a few minutes, then put your finger on it and slowly remove. If bacteria are present strands will adhere to the skin and may stretch up to 1/4 inch long. This is the bacterial ooze that clogs the plant.

Image: Howard F. Schwartz, Colorado State University, Bugwood.org