Chaetocnema confinis Crotch Coleoptera Chrysomelidae

Natural History

Distribution. In the United States, this insect occurs practically everywhere sweet potato is cultivated, including California. However, it is considered a pest east of the Rocky Mountains only, and is not known to be damaging in Canada.

Host Plants. Among vegetable crops, only sweet potato and corn are attacked, and corn only rarely. However, several other crops are sometimes consumed, including clover, oats, raspberry, rye, sugar-

beet, timothy, and wheat. Weeds of the family Convol-vulaceae, particularly bindweed, Convolvulus spp., are the preferred hosts.

Natural Enemies. No natural enemies are known from this poorly studied insect.

Life Cycle and Description. The life cycle of this insect is poorly known. It appears that there is only one generation annually in the north, while several generations may occur per year in the south. The complete life cycle is estimated to require 4-8 weeks for its completion. Adults are found throughout the season, from April through October, but they are damaging to sweet potato foliage principally early in the season.

  1. The egg is deposited in the soil. It is white and elliptical, measuring about 0.2 mm long.
  2. The larvae are white, and likely resemble larvae of corn flea beetle, Chaetocnema pulicara Melshei-mer, or other members of the genus Chaetocnema. Larval development requires about three weeks. The larvae attain a length of about 4.8 mm at maturity.
  3. Pupation occurs in the soil. Pupae are white, resembling the adult in form.
  4. The adult is small, measuring only about 1.5-1.8 mm long. Its color is black, but has a bronze cast. The elytra are marked with rows of punctures. The legs are reddish yellow, and the hind femora are enlarged. The adult is the overwintering stage, and is found under debris and in wood lots near cultivated areas. The adult becomes active early in the year, often in May, and seeks suitable host plants for feeding. Beetles are reported to abandon sweet potato later in the season, as soon as bindweed is available.

There is not a good source of biological information on this insect. Elements of biology can be found in Smith (1910) and Sorensen and Baker (1983).

Plant Pests Vegetable

Damage

Damage by adults is not the typical round-hole injury found in most flea beetles, but rather like that of other Chaetocnema spp. Specifically, they feed in long, narrow strips on the foliage. Often the feeding strips are parallel to the major veins, but as damage levels increase the feeding becomes more general. It is only the young plants that are injured severely.

The larvae are not usually found feeding on sweet potato; the adults apparently prefer to oviposit near bindweed. When feeding on sweet potato, the damage is principally due to consumption of fibrous roots, and larvae do not bore within the roots. Occasionally they etch the skin of the tuber, however, forming winding channels on the surface.

Management

In fields that have a history of flea beetle infestation, pre- and post-planting applications of granular insecticides are recommended (Chalfant et al., 1979a). If systemic materials are not applied, then foliar applications may be necessary to prevent injury to the vines. Some sweet potato varieties are resistant to root injury (Cuthbert and Davis, 1970). Resistant and nonresistant cultivars can be interplanted, with some lessening of injury among interplanted susceptible stock (Schalk et al., 1992). Reduction in larval injury was reported by application of the entomopathogenic nematode, Steinernema carpocapsae (Nematoda: Steinermatidae) (Schalk et al., 1993).

0 0

Responses

  • Susan
    What is chaetocnema confinis (coleoptera: chyrsomelidae)?
    8 years ago

Post a comment