Cucumber beetles are about 6mm long. There are many different types of them. Two of the most common are Striped cucumber beetles and Spotted cucumber beetles.
Spotted Cucumber Beetle (left)-Clemson University, Striped Cucumber Beetle & Spotted Cucumber Beetle (right)-University of Wisconsin
Cucumber beetles are greenish black with yellow stripes or yellow spots. They feed on plant leaves and lay their eggs in the soil beneath the plant. Corn is another favourite of these guys. They will also migrate to your roses.
Lifecycle (left)-University of Virginia, Larvae of Spotted Cucumber Beetle (right)-Seattle Rose Society
Habitat and Lifecycle
Cucumber beetles are everywhere in North America and more prevalent in the southern half. They like good soil and are not usually a problem in sandy soils. They overwinter as adults in very protected areas. They emerge mid spring and find host plants. After mating the females lay their eggs in the cracks of soil around host plants. After hatching the larvae feed on the roots of plants. They pupate in the soil and another generation appears. These guys can be very destructive en masse.
Damage-University of Maryland
Adult cucumber beetles chew ragged holes in the leaves of the plants. Particularly young seedlings. The beetle larva feed on the roots of cucumbers within two weeks of egg laying.
Cucumber beetles also spread plant diseases:
Bacterial Wilt-wilts the leaves and spreads rapidly. Bacterial wilt is fatal and very common. (shown below)
Photo Univerity of Kentucky, R. Besson
Mosaic-makes the leaves mottled, stunts growth and affects the fruit (aphids also can spread this disease)
How To Control Cucumber Beetles
- Get rid of adult cucumber beetles with Liquid Rotenone/Pyrethrin
Mix the powder with water as directed on the label and completely cover the plants with a coarse spray.
- Beneficial Nematodes will get rid of cucumber beetle larvae.
Use Grub-Away® Nematodes Northor Grub-Away® Nematodes South depending on what part of the country you are in. Beneficial Nematodes are parasites that attack certain insects that spend at least part of their lives in (or on the surface of) the soil. They do not harm beneficial insects or earthworms.
- Bt (Bacillus thuringiensis)
Bt applied to the soil in the early spring after the first appearance of adults will also kill the emerging grubs.
- Use a lightweight row cover to protect cucumber plants from adult beetles.
Remove covers at bloom time for plants that need insect pollination. Gardens Alive has a Translucent polypropylene fabric for row covers that transmits 95% of sunlight with almost no heat buildup. They say you can leave this row cover on all summer without harming heat-sensitive plants.
- Plant non-bitter varieties of cucumber
The bitterness in most cucumbers is what attracts these beetles. They have a tendency to avoid most of the non bitter varieties. Sweet Slice and Sweet Success are two varieties that are good choices to plant.
- Plant cucumbers later in the year
Your chances of avoiding this bug though not entirely is to plant later then you would normally.
- Companion planting & Hand picking
Plant radishes nearby. Many times a beetle will prefer those tasty radishes instead and the beetles are easy to see, so handpicking is easy. Pick them off and do the dance of joy on them
Here’s how I controlled them when I lived in a very mild wet climate:
I put down a tomato cage and planted 4 cucumbers around it (so that I could make them climb). In the middle I planted one calendula and surrounded it by radishes. I covered the outside of the cage with cheesecloth leaving the top open. It looked like a tent but it actually worked wonders for me.