Several species populate this family of pest. They include the Striped Cucumber Beetle, which are further divided into the Eastern Striped Cucumber beetle and the Western Striped Cucumber Beetle. Another group are the Spotted Cucumber Beetle, The Western Spotted Cucumber Beetle and the Banded Cucumber Beetle.
Most members of this family attain a length of 1/4 to 1/3 inch. They have moveable mouth parts which enable them to cut and chew plant materials. Their names derive from their coloration which is on their characteristic hard wing covers. They have several different color schemes so there is no single description that covers all species in this family. Most have black heads with antennae.
Cucumber beetles are native to North America and are found in all areas of the United States from Canada to Mexico. They are most abundant and destructive in their southern range. They are generally not a problem in sandy soils. Spotted Cucumber Beetles cannot overwinter in the harsh northern climate zones, but migrate in from their southern range each year. The Striped Cucumber Beetles do overwinter to emerge each spring. All species are strong fliers and when aided by air currents can travel as much as 500 miles in only 3 to 4 days.
Plants of economic impact to humans include the cucurbit species (including but not limited to cucumbers, cantaloupes, winter squash, pumpkin, gourd, summer squash, and watermelon) as well as beans, corn, peanuts, potatoes, and other crops. Overwintering adult cucumber beetles emerge when the temperature rises above 50 degrees F. They feed on up to 200 plant species such as hawthorn and dandelion until cucurbits become available.
Damage description: Damage by cucumber beetles fall roughly into four catagories:
- seedling destruction
- flower and foliage destruction
- root feeding
- transmission of disease
Destruction begins in the spring
when feeding by overwintering adults on the seedling stage of plants occur. The beetles feed on newly emerged cotyledons and stems, and are known to go below ground level to feed on plants as they emerge. After feeding on seedlings for a few days mating occurs. Adult females lay from 200 to 1200 eggs
in the soil near seedlings. Larvae
hatch in 7-10 days and begin feeding on the roots of the plants. The larvae chew holes and tunnel into the roots. Damage by larvae, except under dry conditions, is usually considered minor. The first generation of new adults emerge to feed on the foliage and flowers. Feeding damage to foliage
is usually minor but severe feeding on flowers can result in poor fruit
set. A second generation emerges about 3 months after the first. The entire life cycle
occurs in 6-9 weeks. In northern climes there is only one generation per year, but in the southern range there are 2-3 generations per year.
Usually the worst damage caused by cucumber beetles is from transmission of disease. Bacterial wilt (Erwinia tracheiphila) can kill many plants in a field, seriously reducing yield. Wilt usually starts with a single leaf and spreads to the entire plant, killing it. The growth of the bacteria blocks the channels for sap circulation causing wilt due to lack of nutrients/fluids. Imagine as a comparison a growth in a human arm which blocks blood flow to the limb. Within a short time the arm would die (wilt). Untreated, this condition would lead to the death of the entire organism. Cucumber beetles also transmit squash mosaic virus and various bean viruses. The impact of disease transmission is probably the most important aspect of the cucumber beetle's biology.
Control practices: There are four strategies for control of cucumber beetles.
Row crop coverage
The earliest method that provided good results were reported in 1841. Cucurbit plants were covered with light covers such a cheese cloth which allowed light to enter but which excluded the insects. This method is still employed. Modern row crop covers can provide protection from insects, provide late frost protection and help in moisture retention.
The second method is to employ trap cropping. An early planting of cucurbits can be made to attract the overwintering cucumber beetles where they can be destroyed by insecticides. This reduces the numbers of beetles left to breed and to feed on the main crop planted later. It is necessary to pull out and burn the remaining vines of the trap crop after destroying the beetles. Trap crops are usually not recommended as the sole method used to control cucumber beetles.
A third method is chemical control (pesticides), used particularly in commercial planting. A soil insecticide can be employed at planting time for control of beetles during the seedling stage, and foliar treatments can be applied later in the season as required.
Parasitic control/Predatory Organisms
The use of parasitic organisms such as nematodes has been employed to naturally curb cucumber beetle populations. Other natural predators which help control cucumber beetle populations are bats, soldier beetles, tachinid flies, and braconid wasps.
The identification and control of cucumber beetles is an important part of managing the productivity of a valuable food crop. Unchecked, they can do considerable damage causing economic loss of these important food crops.