Description of black vine weevils
The black vine weevil is an uncommon insect pest in Iowa. It has been reported in only 8 Iowa counties. Almost all reports have come from homeowners who were bothered by the adult weevils appearing as accidental invaders inside the home between October and March. Black vine weevils are oblong oval in shape, about 1/2-inch long and have a short, broad snout with elbowed antennae. The body is slate gray to blackish brown and the wing covers have numerous small pits and patches of short yellow hairs.
Life cycle of black vine weevils
Adult black vine weevils will feed on over 100 different kinds of plants but prefer yews (Taxus) and rhododendrons. Taxus capitata seems to be particularly susceptible to attack. Adult feeding causes small crescent shaped notches along the leaf margins. Black vine weevil adults develop from white legless larvae that live in the soil under infested plants. The larvae feed on young, tender roots. Leaf feeding by the adults seems to have little effect on plant health. Heavy infestations of larvae may cause stunting or death of infested plants.
Damage caused by black vine weevils
Only females are known in North America, and one generation occurs outdoors annually. They are easily transported in potted plants or transplants using a soil root ball. As mentioned, the black vine weevil has been troubling in Iowa as a harmless annoyance indoors after wandering in from infested plants in the landscape. The black vine weevil can not bite, sting or carry diseases. It does not feed on or damage the house structure, its contents or occupants. It is only a pest because of its presence. These weevils can not fly but they are very active walkers. They are most active at night. Black vine weevils found indoors need only be swept or picked up and discarded.
Management of black vine weevils
Spraying is unnecessary and generally ineffective. Susceptible plants in the landscape should be watched for signs of weevil feeding in early summer. Treatment of infested plants in Iowa has not been necessary to this date.
Do you live in Iowa and have an insect you would like identified?
The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them. Please see our website for current forms, fees, and instructions on preserving and mailing insects.
Contact information for each states diagnostic laboratory for U.S. residents. If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.