Vegetable Insect Note 25
Biology
Unmated adults overwinter in neighboring woodlands under leaves
and trash. Adults leave their winter sites in late March and lay
eggs from late April to early June. Before cucurbits are available to
adults, they devour cotyledons and stems. Larvae feed in the
soil on stems and roots, become full grown in two to four weeks, and
pupate in the soil. First generation adults emerge from late
June to early July. A complete life cycle requires from 6 to 9 weeks.
There are two and sometimes a partial third generation each
year.
Adult - The adult spotted cucumber beetle is
about 1/4" (6mm) long with a bright yellowish-green body. The head, legs
and antennae are black, and 12 black spots appear on the wings.
Adult striped cucumber beetles are about 3/16" (5mm) long, black and
yellow in color, and have three longitudinal black stripes on the
wing covers. Both have beaded antennae about 1/16" (2mm) long.
Egg - Eggs are oval, orange-yellow in color, and are found in clusters of 25-50 on undersides of host leaves.
Larva - The larva is 1/3-3/4" (13mm-19mm) long with a yellow-white, somewhat wrinkled body. It has 6 long, brownish colored legs. Striped cucumber beetle larvae are more flattened on the top of the abdomen.Pupa - Colored white to yellow, the pupa is about 1/4" (6mm) long.
Host Plants
Cucumbers, cantaloupes, winter squash, pumpkins, gourds, summer
squash and watermelons are preferred by adult striped cucumber
beetles. They also feed on beans, peas, corn and blossoms of
several wild and cultivated plants. Larvae develop on these and
related cucurbits. The spotted cucumber beetle has a wider host
range and, in addition to cucurbits, may be found on beans, peas,
potato, beet, tomato, eggplant and cabbage. The larvae is the
well-known southern corn rootworm which feeds on the roots of
corn, peanuts, small grains and many wild grasses.
Damage
Adults feed on young seedlings causing poor stands and reduced
yield. They chew leaves and tender shoots, often girdling stems.
They feed in blossoms and late in the season gnaw holes in the
fruit. They are known carriers of bacterial wilt and vectors of
cucumber mosaic.
Control
Several cultural measures discourage cucumber beetles. Early
plowing-discing removes vegetation and discourages egg laying.
Delayed planting (more favorable germinating conditions) and
heavy
seeding rates ensure a good stand. These pests are usually not
as
troublesome in sandy soils. Wire or cloth screen protectors
shaped
like cones or row covers will keep beetles off home plantings
until
plants get established. Early season insect control with seed treated with a neonicotinoid insecticide is strongly recommended.
A foliar insecticide applied at the cotyledon stage will retard cucumber beetle feeding and encourage plant establishment. Where insects are abundant, additional foliar applications may be needed to prevent beetles from spreading bacterial wilt and cucumber mosaic. For information on insecticides and their use, consult the North Carolina Agricultural Chemicals Manual. Be sure to read and follow all label instructions, including intervals between spraying and harvest.
Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data.
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact your county North Carolina Cooperative Extension Service agent.
For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.
Published by North Carolina Cooperative Extension Service
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Web page last updated by M.J. Munster on 24 May 1996