How do I treat cucumber beetles?

Hand-pick in the cool of early morning when they are slow. Row cover from planting until flowering is the most effective measure, since it also prevents wilt transmission.

Will cucumber beetles spread to my other plants?

Yes. Cucumber Beetles spreads, so deal with affected material promptly and keep it out of the compost.

Cucumber Beetles

Q: What causes cucumber beetles?

Cucumber Beetles is pest. The chewing damage is minor. The problem is that cucumber beetles carry bacterial wilt in their gut and transmit it while feeding, and there is no cure for that once a plant is infected. Controlling the beetle is really about preventing the disease, which is why they matter more than their appetite suggests.

Act now

Pest · spreads to other plants · also called striped cucumber beetle, spotted cucumber beetle

The chewing damage is minor. The problem is that cucumber beetles carry bacterial wilt in their gut and transmit it while feeding, and there is no cure for that once a plant is infected. Controlling the beetle is really about preventing the disease, which is why they matter more than their appetite suggests.

What it looks like

Small yellow-green beetles a quarter of an inch long with either three black stripes down the back or twelve black spots. They chew holes in leaves and flowers and drop off the plant when disturbed.

How to confirm it

Yellow-green beetles with black stripes or spots, about a quarter inch.
Drop from the plant when you reach for them.
Holes chewed in leaves and, damagingly, in flowers.
Larvae feed on roots underground, which is invisible until the plant declines.

What to do

1Hand-pick in the cool of early morning when they are slow.
2Row cover from planting until flowering is the most effective measure, since it also prevents wilt transmission.
3Yellow sticky traps reduce numbers.
4Remove any plant that develops bacterial wilt promptly — it is a reservoir.

What it gets confused with

One observation settles each of these.

Squash bugs →

Squash bugs are flat, grey-brown and shield-shaped; cucumber beetles are round, yellow and quick.

Preventing it next time

Cover young plants; they are most vulnerable at the seedling stage.
Grow wilt-resistant varieties where available.
Clear crop debris in autumn.

Plants affected

Cucumber Squash & Zucchini

Check these two things first

Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.

Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.

Not sure it is cucumber beetles? Run the diagnostic key →