Break the cycle of bacterial wilt in your garden

What is happening with my cucumbers? Is there something that I can do for them?

— Jane Mergenthaler, Glendale Heights

The cucumbers in the photo appear to have bacterial wilt, which is caused by the bacterium Erwinia tracheiphila. The leaves of infected plants first appear a dull green, then wilt during the day and recover at night. Leaves eventually become yellow and brown at the margins and then completely wither and die. As the leaves wilt and shrivel up, the stems may dry out suddenly, with the wilting spreading to entire branches and vines. Eventually, the cucumber vine will wither, collapse, and die like the ones in your garden. In plants that are partially resistant, the symptoms can appear as dwarfing along with excessive blooms and branches. The plants will not look normal. Another way to test for this disease is to cut a wilted stem near the base and touch a knife blade to the cut and slowly draw it away. If bacterial wilt is present, you will see white to clear strings of bacterial ooze stringing out from the cut to the knife blade. This test is not 100% reliable.

Bacterial wilt overwinters in the gut of cucumber beetles and is spread by them. Not all beetles carry the bacteria. The beetles that feed on infected plants pick up the bacteria and then move to new plants, creating wounds by their feeding. The bacteria are on the mouthparts and in the fecal matter of the beetles and enter the cucumber vine through the feeding wounds. The bacteria quickly multiply within the plant and plug up the vascular tissue of the vine, which causes the wilting and eventual death of the plant. There is no way to control the disease once a plant is infected. You should remove and dispose of the infected plants in your garden. It is best to put the debris in the garbage and not in your compost pile.

I have not had problems with bacterial wilt of cucumbers in my home garden to date so you may or may not have this recur. Cucumber beetles prefer feeding on stressed plants, so keep your plants well-watered and work carefully around them to avoid damaging the foliage. Look for resistant varieties of cucumbers for your next planting. Monitor your plants in early spring when the beetles appear and start laying eggs on the undersides of leaves. Remove egg sacks as you find them. Early cucumber plantings can be protected with cheesecloth to exclude the beetles. To allow for pollinator access, remove any covers when the plants start flowering. Rotating crops is a good practice but difficult to do in a small home garden if you want to grow cucumbers every year. You can break the beetle cycle by using a three-year rotation of planting cucumbers.

For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.