Cucumber beetles on squash and zucchini
Cucumber beetles are among the most significant pest threats to cucurbits in the eastern US, not primarily because of direct feeding damage -- though that is significant -- but because they vector bacterial wilt, a disease that can kill squash and zucchini plants in a matter of days once.
Cucumber beetles are among the most significant pest threats to cucurbits in the eastern US, not primarily because of direct feeding damage — though that is significant — but because they vector bacterial wilt, a disease that can kill squash and zucchini plants in a matter of days once established. A planting with moderate cucumber beetle activity may suddenly collapse in mid-July when bacterial wilt spreads through a bed, leaving nothing to show for weeks of growth.
I don't grow cucurbits at my Long Island property, so this guide draws on Cornell Cooperative Extension, Penn State Extension, and Clemson HGIC research.
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The pests
Striped cucumber beetle (Acalymma vittatum)
Per Cornell Cooperative Extension, the striped cucumber beetle is the most important cucurbit pest in the eastern US. Adults are 5–6mm, yellow with three black stripes on the wing covers. It is an obligate cucurbit feeder — it does not infest other vegetable families.
Physical barrier beats spraying
Floating row cover blocks cucumber beetles, flea beetles, and cabbage moths before they can lay eggs. Lets in 70% of light so plants keep growing. Read our full pick.
Spotted cucumber beetle (Diabrotica undecimpunctata howardi)
Per Penn State Extension, the spotted cucumber beetle (also called the southern corn rootworm as a larva) has twelve black spots on green-yellow wing covers. It feeds on a wider range of plants than the striped species but also damages cucurbits significantly.
Per Clemson HGIC, the striped cucumber beetle is the primary vector of bacterial wilt; the spotted cucumber beetle can also transmit wilt but is a less efficient vector.