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Cucumber Beetles

Aclymma vittatum and Diabrotica undecimpunctata howardi

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Two kinds of cucumber beetles are poised to eat your seedlings. Worse yet, they transmit bacterial wilt.
Striped cucumber beetle.

Striped cucumber beetle.

Scott Bauer, USDA Agricultural Research Service, Bugwood.org

Description: The striped cucumber beetle, as you might expect, bears three longitudinal stripes down its wings. The spotted cucumber beetle, in contrast, is marked with 12 black spots. Both kinds of cucumber beetle are somewhat oblong in shape with black heads and yellowish bodies. Cucumber beetle larvae are thin white grubs with brown head capsules. Eggs are yellow to orange in color, oval, and found in clusters of up to 50.

Life cycle: Adult cucumber beetles overwinter, usually sheltering in woodlands or dense grasses. They emerge in spring, feeding on pollen and other plants until their preferred cucurbit hosts are available. Once garden crops are planted, the adults move onto cucumbers, squash, and other favorite plants to continue feeding. Mated females lay eggs in the soil below; each female can produce up to 500 eggs. When larvae hatch, they feed on plant stems and roots in the soil before pupating. The next generation of adults emerges in mid-summer, and repeats the cycle.

Crops damaged: Cucumbers, squash, pumpkins, cantaloupe, gourds, and melons. Occasionally also beans, peas, or corn. Spotted cucumber beetles will feed on a wider range of host plants, including tomatoes, eggplant, and potatoes.

Signs and symptoms: Girdled seedlings. Scarring on fruit. Feeding damage to leaves and flowers. Flagging of leaves and eventual vine wilt are signs of bacterial wilt disease, spread by cucumber beetles.

Control measures:

  • Promote good root growth by fertilizing crops properly early in the season. Healthy plants will better withstand cucumber beetle infestations.
  • Use barriers to protect young seedlings from adult beetles. Cones, row covers, or cheesecloth will keep cucumber beetles from feasting until plants are large enough to tolerate them.
  • Delay planting cucurbit crops until later in the season.
  • Remove and destroy and wilt-infected plants immediately.
  • Plant resistant varieties, such as Blue Hubbard squash or Gemini cucumbers.

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