- Pest Type: Insect
- Crops Affected: Soybeans, Corn, Rice
- Scientific Name: Colaspis brunnea
- Pest Order: Coleoptera
Adult grape colaspis beetles are small (4-5 mm), oval, and tan or yellowish-brown. Wing covers appear to be striped cue to the presence of longitudinal rows of shallow indentations. Eggs are smooth, white to yellow, and about 0.6 by 0.25 mm. Larvae are only 3-6 mm long, grayish-white or tan, with a dark brown head and prothoracic shield. These larvae are stout, curved, and grub-like, with three pairs of legs near its head and fleshy appendages on the abdominal segments. Bunches of hairs arise from bumps on the underside of the larval abdomen. Pupae are about 4 mm long and are whitish at first but gradually darken.
Adult beetles are general foliage feeders and the larvae generally feed on roots of the same plants. Soybeans and other legumes are preferred hosts of the adults. The adult beetles rarely do appreciable damage, but when large populations of larvae develop, lateral roots, root hairs, and soft parts of underground stems are consumed. This injury becomes evident above ground as areas of yellow and stunted plants develop; and sometimes purpling of the leaves indicating a phosphorus deficiency, along with browning of the leaf tips and edges. Injury is more severe when weather conditions retard the growth of the seedlings.
The grape colaspis overwinters as small larvae 6-10 inches deep in the soil. In spring, feeding and development resume, larvae pupate 3-6 cm below the soil surface, and adults emerge in only 3-10 days. The adult beetles mate and feed on legumes for several days before laying eggs. Each female deposits about 75 eggs in a couple of masses of about 37 each, near the roots of food plants, and larvae hatch in 7-14 days. In most areas, only one generation occurs per year.
Rotate legume crops with non-legume crops, but this pest seems to have adapted to corn as an alternate host. Rarely have populations of this pest reached levels that require a rescue treatment, and control options are very limited. Contact local advisers concerning recent research results and control recommendations.