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Cucumber beetles

In North America, striped and spotted cucumber beetles feed on squash, cucumbers and melons. Their feeding scars seedlings, and they carry bacterial wilt, which can kill the whole vine.

Pests
A striped cucumber beetle on a cucumber leaf
A striped cucumber beetle on a cucumber leaf

What it looks like

The beetles are easy to spot in flowers.

  • Yellow beetles with three black stripes.
    Striped beetles Yellow beetles with three black stripes.
  • Yellow-green beetles with twelve black spots.
    Spotted beetles Yellow-green beetles with twelve black spots.
  • Holes and scars in seed leaves and stems.
    Scarred seedlings Holes and scars in seed leaves and stems.
  • Whole runners wilt suddenly from bacterial wilt.
    Wilting vines Whole runners wilt suddenly from bacterial wilt.

How to confirm it

Check seedlings and flowers.

  1. Look in flowers

    Beetles gather in open blossoms.

  2. Under leaves

    Beetles drop when disturbed.

  3. Wilt test

    A wilting vine oozing sticky strands when cut points to bacterial wilt.

What to do

Protect young plants.

  1. Row cover

    Cover seedlings with fleece until flowering, then uncover for bees.

  2. Hand-pick

    Knock beetles into soapy water in the cool of the morning.

  3. Yellow sticky traps

    Catch beetles around the crop.

  4. Remove wilted plants

    Pull vines with bacterial wilt promptly.

Prevent it next time

  • Plant resistant varieties.
  • Delay planting until seedlings can grow fast.
  • Clear crop debris in autumn.

What not to do

Do not wait until plants wilt to control beetles; by then the disease is inside.

In the growing guides

Where the guides mention it, with plant-specific advice.

Sources

  1. Cucumber beetles, spotted or striped, on vegetables, University of Maryland Extension
  2. Striped cucumber beetles and bacterial wilt, University of Maryland Extension