Both the spotted
cucumber beetle, Diabrotica undecimpunctata howardii Barber,
and the striped cucumber beetle, Acalymma vittata (Fab.),
are native insects ranging from Mexico to Canada, though they tend
to be most abundant and destructive in their southern range. Striped
and spotted cucumber beetle adults feed on foliage and stems of
young cucurbit seedlings all season long, causing reduced stands.
Adults also harbor the bacterial
wilt organism (Pseudomonas lachrymans) in the winter
and transmit it during the growing season. They also help spread
cucumber mosaic. Larvae injure plants by feeding on the roots and
tunneling through stems.
spotted cucumber beetle is about 6mm (1/4 inch) 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 5mm (../images/16 inch) long, black and yellow in color, and have
three longitudinal black stripes on the wing covers. Both have beaded
antennae about 2 mm (1/16 inch) long. The eggs of both cucumber
beetles are oval, orange-yellow in color, and are found in clusters
of 25-50 on undersides of host leaves. The larva is about 12 mm
(1/2 inch) long with a yellow-white, somewhat wrinkled body and
six long, brownish-colored legs. Striped cucumber beetle larvae
are more flattened on the top of the abdomen. The pupa ranges from
white to yellow in color and is about 6 mm (1/4 inch) long.
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 become 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 six to nine weeks. There are
two and sometimes a partial third generation each year.
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 larva is the well-known southern corn
rootworm which feeds on the roots of corn, peanuts, small grains
and many wild grasses.
on young seedlings, causing poor stands and reduced yield. They
chew leaves and tender shoots, often girdling stems. They feed on
blossoms as well, and late in the season will gnaw holes in the
fruit. They are known carriers of bacterial wilt and vectors of
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 of home plantings until plants are well-established.
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.
Be sure to read and follow all label instructions, including intervals
between spraying and harvest. Some seed catalogs carry resistant
plants which are adequate for homeowner problems with cucumber beetles.
from K.A. Sorensen, North Carolina Cooperative Extension Service,