Typophorus nigritus Crotch Coleoptera Chrysomelidae

Natural History

Distribution. This native insect is recorded from all the southeastern states from Maryland to Texas. It is also known from Central and South America and the Caribbean.

Host Plants. Sweet potato is the principal host of this insect, and the only vegetable crop to be attacked. This species has also been collected from morning-glory, Ipomoea spp.

Natural Enemies. The natural enemies of this insect are not known.

Life Cycle and Description. A single generation occurs annually in North Carolina. Adults are present from late May to mid-July, and eggs from June until early August. Larvae, which are the overwintering stage, are present from June until the following spring. The pupal stage occurs in May. Duration of the complete life cycle is about 300-350 days.

  1. Oviposition occurs about 14 days (range 10-22 days) after the adults emerge and commence feeding. The eggs are elongate-oval and measure 1.36-1.44 mm long and 0.56-0.64 mm wide. Eggs are yellow and are deposited in clusters of 3-25. Eggs normally are deposited in the soil, but sometimes on foliage, and females reportedly produce an average of 50 eggs. Duration of the egg stage is 6-10 days.
  2. Upon hatching, the larva enters the below-ground portions of the vine or the roots to feed. The larvae are pale yellow, with a brownish head. The larva is only about 1.5 mm at hatching, but grows to
Typophorus Nigritus
Sweetpotato leaf beetle larva.

about 11 mm at maturity. The larval period, which includes the overwintering period, is 260-320 days.

  1. Pupation occurs in the soil in cells at a depth of 10-20 cm. The pupa resembles the adult in form except that the legs, antennae and wings are folded closely to the body. The pupa is pale yellow or white and measures 7-8 mm long. Duration of the pupal stage is about 18 days. Newly molted beetles remain in their pupal cells for 4-5 days before digging to the surface of the soil.
  2. The adult is oval and metallic bluish-green to black. The antennae are reddish. The elytra are rather smooth. The beetles measure 6.0-7.5 mm long and 4-5 mm wide. Adults commence feeding on foliage about two days after emergence and live for 3040 days. They drop from the foliage to the soil surface if disturbed, and sometimes are found hiding in leaf litter during the daylight hours. The duration of the oviposition period is about 30 days.

The biology of sweetpotato leaf beetle was presented by Brannon (1938), and additional observations could be found in King and Saunders (1984).

Damage

The adults feed on the foliage, starting with the marginal areas and working inward toward the center of the leaf. The aggregated nature of adults, especially

after they have initially emerged, tends to result in localized defoliation. However, adult feeding damage is relatively minor as compared to injury by larvae. The larvae feed in stem, root and tuber tissue. Larvae can burrow deep into the tuber, creating tunnels packed with fecal material. They also may conine their feeding to the surface of the tuber, creating scars.

Management

These insects, while widespread, are infrequently numerous. Therefore, controls are rarely warranted. Foliar insecticides effectively suppress adults. Larval injury is best prevented with the application of liquid or granular insecticide to the soil.

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