Gratiana pallidula Boheman Coleoptera Chrysomelidae

Natural History

Distribution. The eggplant tortoise beetle is found widely in the United States, from Maryland to Florida in the east, and west to California. A native species, eggplant tortoise beetle is most common in southern states, and is not known as damaging in northern states and Canada. A strikingly similar insect, G. lutescens (Boheman), is common in South America and interbreeds successfully with eggplant flea beetle, so the status of these species is uncertain (Siebert, 1975).

Host Plants. This species feeds on plants in the family Solanaceae. In addition to eggplant, potato, and tomato, eggplant tortoise beetle has been collected from horse nettle, Solanum carolinense; silverleaf nettle, Solanum elaeagnifolium; and nightshade, Solanum sp.

Natural Enemies. An unspecified egg parasitoid was noted by Jones (1916b). A pupal parasitoid Spilochalcis sanguiniventris (Cresson) (Hymenoptera: Chalcididae) also is known, but its significance is uncertain.

Life Cycle and Description. The number of generations per year is about five in Louisiana. A complete life cycle requires about 30 days. The insects are active from May to October.

Egg. The egg is elongate oval, measuring about 1.24 mm long (range 1.16-1.30 mm) and 0.67 mm wide (range 0.62-0.76 mm). The egg is whitish initially, but turns brown with age. Eggs generally are deposited on the underside of foliage, but sometimes elsewhere. Eggs are deposited singly or in small clusters of 2-4, and covered with 1-2 layers of brownish adhesive. Fecundity is estimated at 250 eggs or more. Duration of the egg stage is generally 4-5 days.

Adult striped tortoise beetle.

ous small- or medium-sized irregular holes. The leaf may be completely riddled with holes, but the major veins are left intact. Both stages usually inhabit the lower surface, but eat entirely through the foliage. The tortoise beetles are rarely abundant enough to be considered damaging.

Management

The larvae and adults are easily controlled with foliar insecticides, but this action is rarely warranted.

Larva. The larvae are light green or yellowish green. The surface of the body is equipped with about 16 pairs of branched spines occurring laterally. The tip of the abdomen also bears a pair of spines called the "anal fork," which collects the shed cuticles and excrement. The anal fork bearing debris may be held over the body, presumably providing camouflage or physical protection from natural enemies. There are five instars. Larval head capsule widths are about 0.46, 0.55,0.67,0.82, and 0.97 mm, respectively. Mean development time of larvae is about 17 days (range 12-20 days). Larvae eventually attain a length of about 5.0-5.5 mm.

Adult eggplant tortoise beetle.
  1. Pupation occurs on the foliage, where the pupa is attached by the anal region. The pupa measures about 5.4 mm long, and retains most of the branched spines present on the larva. Duration of the pupal stage is 4-7 days.
  2. The adult is oval, and measures about 5.0-6.0 mm long. It is greenish or yellow-green, with yellowish-brown appendages. The elytra bear several rows of coarse punctures. Adults normally live 2-3 months.

The biology of eggplant tortoise beetle was described by Jones (1916b).

Damage

The larvae and adults occur on the foliage of solanc-eous species, where they feed and create small, somewhat circular holes. Unlike feeding by most flea beetles, with which tortoise beetle injury could be confused, eggplant tortoise beetle feeds completely through the foliage. This insect is rarely considered damaging, and is usually restricted to eggplant.

Management

Foliar insecticides are effective against both larval and adult stages of this insect.

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