Cucumber Beetles

Tuesday, June 19th, 2012 by Jenny Watts
    • Set out zinnias, cosmos, impatiens and begonias for lots of colorful flowers all summer long.
    • Star jasmine is an evergreen vine that prefers some shade. The fragrant blossoms fill the June air with their sweet scent.
    • Finish planting the summer vegetable garden. Seeds of early corn, and beans can go directly in the soil and plants of tomatoes, peppers, eggplant, melons, squash, cucumbers and basil can be set out.
    • Spray roses every two weeks with Neem oil to keep leaves free of black spot and mildew.
    • Water lawns deeply, preferably in the early morning hours. Set mower blade to the highest position to reduce moisture loss during the summer.

Cucumber Beetles

Late spring marks the arrival in our area of the Spotted Cucumber Beetle. This little green beetle looks a bit like a green ladybug, but it is not one of the “good guys.” They can do a lot of damage to your vegetable garden in a short time.

Cucumber beetles are a major pest of cucumbers, squash, melons, watermelons and gourds. They particularly like the tender parts of plants, like the flowers, which they may destroy with their feeding. They also feed on stems of young plants, chew holes in leaves and can damage young fruits. They will also attack flowers in the garden like roses, dahlias and zinnias, making unsightly holes in the petals.

Cucumber beetles overwinter in the adult stage in nearby weedy areas, and become active at about the time that the earliest cucurbits are transplanted or seeded, when temperatures reach 55 to 65 degrees. They may feed on alternate host plants until cucurbit plants appear. The adults lay eggs at the base of plants, and as soon as they hatch, the larvae begin feeding on plant roots. The larvae are sometimes called rootworms.

In addition to these visible signs, cucumber beetles can spread plant diseases, such as bacterial wilt, squash mosaic virus, and others.

Although cucumber beetles are common every year, their damage tends to be severe only some years. Heavy populations feed mostly on flowers of squash, melons and cucumbers.

A variety of methods can be used to keep the beetles under control. Floating row covers, made of polyester fabric, can prevent adult beetles from landing on plants in the spring. These thin blankets of woven polyester allow water and light to pass through but keep insects out.  Cover the plants loosely with the fabric and seal all the edges with soil. Remove the covers when plants start to bloom to allow the flowers to get pollinated.

Straw mulch discourages egg laying, for the one or two more generations that can occur through the summer, and attracts predatory spiders and ground beetles. But mulch should be avoided if you also have squash bugs, which it will attract.

You can also set out yellow sticky traps, which will attract and capture the beetles. Check the traps to make sure that they are not catching beneficial insects as well. If they are, it’s best to remove them.

Some flowers, such as yellow and orange zinnias, make fine cucumber beetle traps. They will congregate on the flowers, then when the temperatures are cool, you can vacuum the beetles up when they are moving slowly.

The cool of the morning or evening is also the best time for hand-picking. Carry a pot filled with a soapy water, jiggle of the plants, and the beetles will drop off the plants into the water and drown.

Neem oil has been shown to act as a repellent for cucumber beetles. The foul odor seems to keep them from feeding on the plant leaves. Spraying once or twice a week will stop the beetles from further invasion.

Take action now to keep cucumber beetles from becoming a real problem in your garden.