Ornamental & Turf Insect Note Logo

WHITE PINE WEEVIL

James R. Baker and S. Bambara, Extension Entomologists

CAUTION: This information was developed for North Carolina and may not apply to other areas.

WHITE PINE WEEVIL, Pissodes strobi Peck, Curculionidae, COLEOPTERA

General Information

legless grubThe white pine weevil is a small (3/16 to 1/4 inch), brownish beetle with a curved snout that is almost as long as the rest of the body. The wing covers are spotted with brown and white scales. White pine weevil eggs are small, pearly white and translucent.

Mature larvae are yellowish-white, legless grubs with brown heads. They are 3/16 to 1/4 inch long. White pine weevil pupae are creamy white and 3/16 to 1/4 inch long. This insect is also known as the sitka spruce weevil and Englemann spruce weevil.

Biology

grub close upWhite pine weevils occur throughout eastern North America within the range of the primary host plant, white pine (Pinus strobus). This weevil infests other pines and spruces, especially Norway spruce. The white pine weevil kills the top (two to five years of growth) of pine and spruce trees as the larvae bore in the bark and wood.

In mid June, infested branches begin to wilt. One or more of the top branches grow upward to replace the leader which results in a crooked or multiple trunk tree. Adults feed on the buds and bark to a limited extent.

Adults overwinter in litter. In mid to late spring after new growth has emerged on white pines, the adults emerge and crawl or fly to the new top growth. These weevils feed on the succulent bark 7 to 10 inches below the top most bud. Eggs are deposited in a ring around the leader in about a week. The larvae hatch 1 or 2 weeks later. The larvae often work downward as they feed on the cambium, completely girdling the leader. As they mature, the grubs burrow into the pith and form a pupal cell. Some grubs form chip cocoons just under the bark. Two weeks later the grubs pupate. Then after twelve more days the new adult molts from the pupal skin. Development takes 7 or 8 weeks. The new adults eventually chew out through the bark of the dead leader and feed for a short time on the new buds or young growth. They then seek an overwintering site even though the weather may be warm.
To help confirm that white pine weevil is the cause of the dead white pine or spruce top, use your fingernail and scrape back the bark in the affected area. The bark will be very loose and a dark, moist, powdery material will be present under the bark. As you scrape further down, you should find oval patches of excelsior-like material, about 1/2-inch long. After removing this material from the patch, you will find an area in the sapwood that has been hollowed out. This is the "chip cocoon" of the weevil. You may even find the pupae or yet-to-emerge adults within the cocoon.

Control

Control of the white pine weevil depends upon the stage at which they are found. If an infestation of grubs is found, the infested portion of the leader should be pruned out and only one of the branches in the top (living) whorl of branches should remain so that this branch will grow upwards to replace the leader. This will result in the least disruption of orderly growth and shape.

Following the emergence of new tree growth, if feeding punctures from the adult are observed, a pesticide may be sprayed on the leader to protect it from egg laying. Chemicals containing cyfluthrin or diflubenzuron may be useful protectants when timed correctly. Whenever adults are observed on the leaders of small white pines, adult weevils may be collected by jarring the tree, causing the weevils to tumble down. The weevils may be destroyed by drowning them in a solvent or by some other means. Tests in Ohio are showing some protection with imidicloprid.


  More information on this insect may be found in:
USDA FDI Leaflet 21
Ohio State Information Note

Other Resources

For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service.

Prepared by: James R. Baker & S. Bambara, Extension Entomologists
Some information provided by Dave Shetlar, Ohio State University


Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

© 2001 NC Cooperative Extension Service


ENT/ort-33 August 1994 (Revised) May 1997
Web page last reviewed January, 2011 by the webperson.