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Squash Bug

Anasa tristis

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Squash bugs suck sap from squash, pumpkins, melons, and other cucurbits in the home garden.
Squash bug.

Squash bug.

Whitney Cranshaw, Colorado State University, Bugwood.org

Description: Like many true bugs, squash bug adults are flat with wings that fold over their backs. The edges of their abdomens have light orange stripes, but otherwise, these pests are black or brown. Newly emerged nymphs are greenish in color with black heads and legs. As they progress through five instars, the young bugs darken to their adult colors. Squash bug eggs, found in clusters on the undersides of foliage, are bronze or yellow.

Life cycle: Adult squash bugs overwinter by seeking shelter in leaf litter, garden debris, woodpiles, or other protected places in the yard. When vines begin running in early summer, these adults mate and lay eggs on host plants in the garden. Eggs hatch in about 10 days. Nymphs develop over the course of 4-6 weeks. In late summer, it's common to observe eggs, nymphs, and adults together in the garden, as generations overlap.

Crops damaged: Squash and pumpkins. Sometimes gourds, melons, or cucumbers. Both adults and nymphs damage plants by sucking on sap.

Signs and symptoms: Yellow spots on foliage of susceptible plants. Wilting or withering vines. Spots or entire vines turning black.

Control measures:

  • Hand pick adults and nymphs, dropping them in a can of soapy water to destroy them. Squash bugs flee and hide when disturbed, so this is easier said than done.
  • Use trap boards on cool nights in spring to collect squash bugs. Check under boards in early morning before bugs become active, and destroy any gathered underneath.
  • Monitor plants for eggs, and crush any squash bug eggs present.
  • Remove and destroy vines immediately after harvesting fruit to discourage squash bugs late in the season.
  • Limit places where squash bugs can shelter in the garden.

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