Department of Entomology
Entomological Notes
Black Vine Weevil
Otiorhynchus sulcatus Fabricius
The black vine weevil is a serious pest in nurseries and established landscape plantings. A native of Europe, this species was first reported in Connecticut in 1910. This key pest is the most destructive and widely distributed species of root weevils in the genus Otiorhynchus . Adults and larvae prefer rhododendron, Rhododendron spp., yew, Taxus spp., euonymus, Euonymus spp., and Japanese holly, Ilex crenata . Larvae also feed on the roots of hemlock, Tsuga spp. This pest has been recorded on more than 100 species of cultivated and wild plants. Some landscape pest managers refer to this insect as the taxus weevil.
Description
The larval (grub) stage of this pest is white, legless, somewhat C-shaped with a brown head. Adults are slate gray to black, flightless, about 9-13 mm long, and have a short pronounced snout with elbowed antennae. Their front wings are covered with tiny concave areas and small patches of short golden hairs (Fig. 1). The strawberry root weevil, O. ovatus, closely resembles this species, but it’s only half the size of the black vine weevil.
Figure 1. Adult black vine weevil.
Life History
This pest overwinters as immature larvae in the soil. Mature larvae are 10-15 mm long and form resting (pupal) cells in the soil in early spring. Adults usually emerge from late May through June and in North America only females are known. They are active night feeders and when disturbed, adults drop quickly to the ground. During daylight hours adults hide in dark places on stems of plants with dense foliage or in leaf litter and mulch.
Adults require 21-28 days of foliage feeding prior to producing eggs. They may lay as many as 500 eggs over a period of 14-21 days. Eggs are laid in the soil near the base of host plants. They hatch in 10-14 days into small larvae that feed on roots until fall temperatures cause them to move deeper into the soil where they overwinter. Occasionally, a few adults may survive the winter inside homes. Only one generation occurs each year in Pennsylvania.
Damage
Injury caused by the larval stage feeding on the roots is highly destructive to plants. Feeding by larvae occurs from mid-summer through fall and in early spring. At first larvae feed on small tender roots, but in early spring, they move to the bark of large roots or the stem, sometimes completely girdling them. Damage to roots may go undetected in nurseries, but infested plants that are placed in landscapes often die. Injury caused by adults is in the form of marginal notching of broadleaved evergreen foliage and other host plants. This foliar damage seldom impacts plant health, even though it may be extensive.
Management
Manage adults by applying a registered insecticide according to label directions to host plant foliage during late May through June. Optimal timing of an application against the adult stage of this key pest may be achieved by doing the following. In early May place 6-inch by 6-inch boards on top of the mulch beneath several host plants. Pieces of burlap placed loosely around the base of a host plants may be substituted for the boards. During the middle of the day slowly turn over these boards or burlap. Note when you observe the first adult black vine weevil on the bottom of one of these monitoring surfaces. Because adults need to feed on foliage for 21-28 days before they’re able to lay eggs, the first foliar application should be made three weeks after detection of the first adult. Since adults do not emerge at the same time, a second foliar spray should be applied according to label directions three weeks after the first one. Spraying foliage in early evening may increase control because adults become active on the host foliage a few hours after sunset.
Applying registered materials according to label directions as soil drenches to container-grown plants from July to mid-October target the larval stage of this pest. The use of beneficial (entomopathogenic) nematodes applied according to label directions may be used to manage the larval stage of this pest in container-grown plants. Be sure to apply water as directed on the product label to the potted plants to be treated with these organisms.
Warning
Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.
Authored by: Gregory A. Hoover, Sr. Extension Associate
December 2000
DISCLAIMER
This publication is available in alternative media on request.
Where trade names are used, no discrimination is intended and no endorsement by The Pennsylvania State University or Pennsylvania Department of Agriculture is implied.
Entomological Notes are intended to serve as a quick reference guide and should not be used as a substitute for product label information. Although every attempt is made to produce Entomological Notes that are complete, timely, and accurate, the pesticide user bears the responsibility of consulting the pesticide label and adhering to those directions.
Issued in furtherance of Cooperative Extension Works, Acts of Congress May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture and the Pennsylvania Legislature. D. Jackson, Director of Cooperative Extension, The Pennsylvania State University.
The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-2801; Tel 814-865-4700/V, 814-863-1150/TTY.
