Here are tips on how to identify, eliminate, and control cucumber beetles.
What are Cucumber Beetles?
If you find that the stems of your seedlings are being eaten off, leaves are yellowing and wilting, and holes are appearing, you may have a striped cucumber beetle.
Cucumber beetles are found throughout the US and cause much of the same damage as flea beetles do. They are attracted to Cucurbit vegetables, namely cucumbers, squash, pumpkins, and beans.
Often, the beetles leave their hibernating sites early in the season, and feed on seedlings right as they are emerging, often killing them. The larvae feeds on the roots of the host plants. Adults will also feed on the leaves, vines, and fruit of plants that survive, often making deep marks in the rind.
They hold another threat too: the can carry bacterial diseases and viruses from plant to plant, such as bacterial wilt and mosaic virus.
How to Identify Cucumber Beetles
Adults are about ¼ inch long and have a yellow and black striped abdomen and a dark colored head and antennae. Look for holes and yellowing and wilting leaves. Crop yield will be low; and plants will produce yellow and stunted fruits. The larvae are worm-like, white, dark-headed, and have three pairs of legs on the thorax.
Often, the cucumber beetles alone will not kill the plants or cause major damage, but the spread of disease will. Adult cucumber beetles overwinter in weeds, garden debris and woody areas. The diseases they carry can also overwinter internally, and can be passed onto plants the next spring through fecal matter.
How to Control Cucumber Beetles
Inspect newly planted cucurbit plants for the presence of this beetle; be watchful when plants are seedlings.
Cover seedlings with row covers, though you rmust remove during blossoming time several hours each day to allow pollination.
If you till your garden in the late fall, you will expose cucumber beetles hiding there to harsh winter conditions and reduce their populations next year. Tilling has the added benefit of making the soil easier to work in the spring.
Where cucumber beetles are a problem, let the beetles come out of hiding and plant late. They have a knack for finding vulnerable seedlings. When yours are up and growing, the cucumber beetles will be gone, fooled into thinking you don't have any cucumbers in your garden.
Few insecticides can be used on cucurbit plants because they are very sensitive. They would need to be used when plants are beginning to emerge through the soil. Please contact your local cooperative extension for a list of approved insecticides for your area.
Natural predactors include soldier beetles, braconid wasps, some nematodes, and soldier beetles.
Once bacterial disease has entered the plant, there's very little that you can do. If it's bacterial wilt, you'll see the leaves dry up and the plant will quickly wilt and die. Take prevention for next year as described above.