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Cucumber Beetle

Closer Look Of The Cucumber BeetleThe cucumber beetle damages vegetable crops by chewing the leaves and roots, retarding development or even killing young emerging plants. They can also spread diseases such as bacterial wilt and cucumber mosaic virus. Amassing in large numbers, they can attack and chew the fruits of vegetables.

The most common beetles have small yellow and black stripes, being only about 1/4” long. The adults eat plant leaves or stems for several weeks, then drop to the ground and lay their eggs in cracks around the base of the plant. When hatched, the larva crawls towards the roots of the plant, attacking it from below, feeding for about a month or so.

Spotted cucumber beetles are somewhat larger and prefer to feed on corn. When the larva of these insects attack corn roots, they are known as ‘corn rootworms’.


Adult Striped And Spotted Cucumber BeetleThese small beetles are normally yellowish green with black spots or stripes. They mate immediately upon emerging from the ground, and the females lay their eggs in cracks or crevices in or near the base of the plant. Some adult beetles will over winter in litter or spent vines in wooded areas, and will emerge in spring; others will simply fly in from southern states, being able to fly 100 miles in a single day.

The adults carry a bacterial wilt in their feces, which, when infected, will cause the plant to wilt and die before bearing fruit. The mosaic virus is carried in the stomach (gut) of the insect and spreads when the insect chews leaves and stems.


Cucumber Beetle EggsSome beetles lay their eggs – up to 800 of them - at the base of corn stalks in September and October, and hatch the following spring. Others will lay eggs at the plant base later in the season, when a second crop of insects will emerge. When the yellow oval eggs hatch, about 10 days later, they burrow down underground and attack the roots of the corn. There is normally only one generation of insects in the north but two or more in southern states.


Cucumber Beetle LarvaeThe larval stage of this insect likes to feed on the roots of crops for two to six weeks, and then enters the pupa stage of its life. The caterpillars are slightly larger than adults, being about 1/3 to 1/2 of an inch long and are normally very slender and white in color, brownish at the ends. They can destroy the entire root system or stem of the plant, but more mature plants can usually tolerate this damage.


Cucumber Beetle PupaThe young larvae feed on the roots and stems of the plants for about a month, then enter the pupa stage of their lives. They remain in this stage for several weeks and then emerge from the ground as adult insects, where they begin feeding on the leaves and fruits of the plants.

Vegetables That Cucumber Beetles Like To Eat

Asparagus Corn Peas Pumpkins
Beans Cucumbers Peppers Squash
Beets Eggplant Potatoes Tomatoes


Floating Row Cover Over The PlantsUsing a floating row covers over your crops, when possible, greatly reduces the likelihood of a beetle infestation (see picture at left). Timing is important, because if you can destroy the first generation of insects, any others that will appear later will do little damage.

If you put a mulch around your vegetables, the adults have a difficult time locating the base of the plant to lay their eggs, and many will die. Be sure to clean up all garden debris in fall, as the beetle likes to over winter in such sites.

Try intercropping cucumbers with other plants, especially radishes, but marigold flowers, corn or broccoli also seem to work. Research has suggested that the beetles have difficulty locating the cucumbers and will leave the area sooner when these crops are present.

If all else fails you can use carbaryl, rotenone (1 percent solution) or sabadilla for very heavy infestations. If you must do this, cover the cucumbers with floating row cover to keep beneficial insects, like bees, away from the flowers. Remove the covers after three days. Spraying the tops and bottoms of leaves with mix #24, has also been reported to be very effective.

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