Cucumber Beetles: How to Control Them Naturally

Cucumber Beetles

Acalymma vittatum (striped), Diabrotica undecimpunctata (spotted), Diabrotica balteata (banded)

Small striped or spotted beetles that chew cucumber, squash, and melon plants and spread bacterial wilt.

How to control cucumber beetles

Use: Scanmask Spray (also works: Ecomask Spray, Scanmask Topdressing, Ecomask Topdressing)
When: March to July.
Where: Spray the soil in a band around the base of cucumber, squash, and melon plants, and water it in.

What it looks like

Adults are about 1/4 inch long and yellow-green, with black stripes (striped), 12 black spots (spotted), or green bands (banded). Larvae are slender, white, worm-like grubs with a brown head that live in the soil.

Illustration of an adult spotted cucumber beetle seen from above, a yellow-green beetle with twelve black spots on its back Illustration of an adult banded cucumber beetle seen from above, a green beetle with yellow bands across its back and a reddish head

A spotted cucumber beetle (left) and a banded cucumber beetle (right). The picture at the top is a striped cucumber beetle.

Damage

Adults chew seedlings, leaves, and flowers and spread bacterial wilt, which can kill vines. Larvae feed on roots and on the underside of fruit touching the soil.

How nematodes help

The eggs are laid in the soil at the base of the plant. The larvae feed on roots and turn into pupae in the soil, where nematodes can reach them. Nematodes don't reach the adults on the leaves.

A Penn State field study found that nematodes cut the number of striped cucumber beetle larvae that survived by half and helped cucumber roots grow better. Several Steinernema species did well in lab tests, though the species used in the field was S. riobrave (a species BioLogic doesn't sell).

In university research, the timing that worked best was late spring to early summer (May to July), about 1 to 3 weeks after the adults first show up, when the larvae are in the soil. Treat again for a second generation in mid to late summer.