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Cucumber Problems - Bacterial Wilt?

What Causes My Cucumber Vines to Die Off?

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Stripped Cucumber Beetles

Stripped Cucumber Beetle

Photo Courtesy of the USDA Agricultural Research Service. Used with Permission.

Cucumber vines that mysteriously wilt and die off are probably infected with bacterial wilt. Cucumber bacterial wilt is transmitted by the cucumber beetle. There’s not much you can do once the vines are infected with cucumber bacterial wilt, but you can take some measures early in the season to protect your young cucumber plants. Here’s help for cucumber bacterial wilt.

Symptoms of Bacterial Wilt

The plants wilt even when they’ve been well watered. You can test cucumbers by cutting a badly wilted stem just above soil level and squeezing it. If a sticky, oozy substance comes out, it’s bacterial wilt. This slimy substance is clogging the plant’s circulatory system, so the plant can’t take in the water it needs.

The damage happens quickly in cucumbers and muskmelons. Within a week of infection, you may start to see dull patches on the leaves. Within 2 weeks the entire vine will be wilting and the fruits will start to look small and deformed. Very often there is no yellowing of leaves. Squash are slowly to show symptoms, but growth may slow.

Plants Affected by Bacterial Wilt

Members of the curcurbit family: cucumbers, melons, squash, pumpkins and gourds

Causes of Bacterial Wilt on Cucumbers

A bacteria, Erwinia tracheiphila, which is spread when the striped cucumber beetle or the spotted cucumber beetle feed on the plant’s leaves. The bacteria can overwinter in the beetle’s or they may pick it up while feeding elsewhere. These beetles can also spread cucumber mosaic virus.

The stripped cucumber beetle, shown right, is about 1/4" (6 mm) long with 3 black stripes on its yellow-green wings.

The spotted cucumber beetle is a similar yellow-green color with twelve black spots. Spotted cucumber beetles feed on more types of plants than just curcurbits.

The larvae of both beetles are white with darker heads and posteriors and can be found in the soil under your cucumber plants. The eggs are a bright orange-yellow.

Controlling Cucumber Bacterial Wilt

  1. Healthy Plants: For starters, cucumber beetles prefer feeding on wilted plants and wilted plants are already more prone to infection. Keep your plants well watered and healthy. The bacteria needs a wound, like a deep beetle bite or a tear, to enter through, so avoid damaging your cucumber plants.

  2. Resistant Varieties: Choose cucumber varieties that are more tolerant of cucumber beetles, like ‘Liberty’ and ‘Wisconsin SMR58'.

  3. Monitor Early: However keeping the beetles out of your garden is your best control. The beetles show up in early spring and lay their eggs on the undersides of the leaves. Keep an eye out for signs of the beetles, as soon as your cucumbers are planted. Monitor the leaves and destroy any egg sacks by removing or squashing.

  4. Barriers: You can protect early cucumber plantings by covering the plants with a floating row cover or cheesecloth. Secure the bottom of the cover, because beetles will crawl under it. Just be sure to remove the cover when the flowers appear.

  5. Pesticides: Cucumbers are very sensitive to pesticides, so use them as a last resort and follow the label directions. Stripped cucumber beetles are most active from dusk to dawn, so spraying in the evening is most effective. Rotenone and insecticides containing pyrethrin are recommended.

  6. Predators: There are a few natural predators. The tachinid fly and braconid wasp will offer some control as will one species of soldier beetle.

Once the Cucumber Vines are Wilted

If your vines should become infected, they will need to be pulled and removed. There is no cure for bacterial wilt. Remove all the vines in the fall.

Sources:

  • Bacterial Wilt of Curcurbits, County Commissions, North Dakota State University and U.S. Department of Agriculture

  • Cucumber Beetles, Corn Rootworms, and Bacterial Wilt in Curcurbits, Cornell University VegetableMD Online

  • The Organic gardener’s Handbook of Natural Insect and Disease Control, Ed. Barbara W. Willis & Fern Marshall Bradley, Rodale Press, 1996

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