Vegetable Weevil
Listroderes costirostris obliquus (Klug), Curculionidae, COLEOPTERA


DESCRIPTION

Adult - The female adult weevil is about 6.4 mm long with a short, stout snout. It is a dull grayish-brown with a light V-shaped mark on the wing covers.

Egg - The egg is elliptical, 0.5 mm in diameter, and creamy white when first laid. It becomes black before hatch.

Larva - The pale green, legless larva has a dark mottled head, and is about 1 cm long when fully developed.

Pupa - The pupa is pale yellow at first and later turns brown. It is similar in shape to the adult, with snout, legs and wing pads folded around the body. It is about 7.9 mm long.


BIOLOGY

Distribution - The vegetable weevil, originally from South America, was first reported in this country in 1922. It now occurs in the Gulf and southern states and in Oklahoma, Arizona, and California. In North Carolina the vegetable weevil occurs throughout the state but is generally more common in the southern Coastal Plain.

Host Plants - The vegetable weevil feeds on a wide range of cultivated crops: turnip, carrot, collard, mustard, tomato, potato, tobacco, and also a number of weeds.

Damage - Larval and adult vegetable weevils attack the foliage and roots of a number of vegetable crops. In tobacco plant beds both larvae and adults attack the seedlings and both may attack newly set plants in the field. Larvae feed both on the buds, stunting growth, and the leaves of seedlings. Their feeding causes irregularly shaped holes in the leaves.

Life History - The adult vegetable weevil is active during fall, winter, and spring and aestivates (enters dormancy) during the summer in trash, leaves or grass at the edges of fields. Reproduction is parthenogenetic (no males, females lay eggs which develop into females) and some individuals may live two years. After coming out of aestivation, adults feed for several days to a month before depositing eggs on turnips or collards. Oviposition begins in fall and may continue into spring of the next year. Hatch occurs after an incubation period of two or more weeks depending on the temperature. Larvae feed on tobacco seedlings (and other vegetable crops) and become fully grown in 23 to 45 days. Pupation occurs in earthen cells in the soil in spring or in fall and late winter and will last from a few days to two weeks depending on the temperature. Adults emerge from January to June. The length of time from egg hatch to adult emergence may vary from 1 to 4 months. There is one generation per year.


CONTROL

Cultivation in fall and winter is important in reducing populations. Insecticides are also available for control of the vegetable weevil. Treatment should begin when 5 percent or more of small, newly set plants (within 3 weeks after transplanting) are killed or injured. For specific recommendations, consult the current North Carolina Agricultural Chemicals Manual.