integrated pest management

Black Vine Weevil
Otiorhynchus sulcatus

The adult weevil is approximately 3/8 inch in length and brownish black. Small patches of golden scales are scattered on the wing covers. The adults are nocturnal feeders. The head of the adult projects into a long, broad snout. The larva are white, legless, grubs approximately 3/8 inch long when mature, and have a dark head.

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Black Vine Weevil Pupa and Larva
Figure 1. Black Vine Weevil Pupa (left) and Larva (right)

Life History
Only one generation of the weevil occurs outdoors, annually. The adults appear during June and early July. They feed on foliage at night by cutting characteristic U-shaped notches in the foliage of the host plant. During the daylight hours the adults hide in the debris and loose soil at the base of the plant. Eggs are laid during July and August in the soil under the plants on which the adults feed. As the eggs hatch the larvae burrow into the soil and feed on the roots. They overwinter in the soil as full-grown larvae and develop into pupae in late May or early June. Eggs are deposited without fertilization and only females are produced. No males have been observed with this species. The beetles cannot fly, so infestations spread slowly from one area to another. However, rapid spread may occur in a localized area.

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Black Vine Weevil Larva and Damaged Root
Figure 2. Black Vine Weevil Larva and Damaged Root

The black vine weevil feeds on over 100 different kinds of plants including flowers, weeds, trees, and woody ornamentals. yew (Taxus spp.) appear to suffer the greatest damage from larval root feeding. Taxus capitata seems to be particularly susceptible. Heavily infested plants turn yellow and eventually die if the injury continues. The economic importance of this insect has increased because of the increased popularity of various species of Taxus for ornamental purposes and the increase in size and number of Taxus plantings in nurseries. In some cases, hundreds of plants have. been killed suddenly just after reaching a marketable stage.

Nonchemical Control
Isolation of infested plant material will greatly reduce the spread of blackvine weevil larvae. Predaceous nematodes are available for control of the larvae in containers and landscape beds.

Chemical Control
Insecticidal sprays may be applied to the foliage in mid-May when adult are present on the foliage allowing the spray to run off onto the soil under the shrubs. Treatments should be repeated twice at 2 week intervals.

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Black Vine Weevil Adult and Damage on Yew
Figure 3. Black Vine Weevil Adult and Damage on Yew