Contents: By Damage and Image
Poplar and willow borer
A cryptic weevil as an adult, the damage from the poplar and willow borer, Cryptorhynchus lapathi, is all too obvious. This borer can infest in high numbers in preferred hosts causing high levels of mortality to a stand. Hosts include willow, poplar, alder, and birch. Willow is the preferred host, but hybrid poplar stands can suffer heavy losses. Solomon (1995) reports that balsam poplar and black cottonwood are susceptible while quaking aspen, alder, and birch are rarely attacked.
Both adults and larvae can overwinter in Canada and so are likely to do so in areas west of the Cascades. Summer into fall is the period when adult weevils emerge. The adults are most active in the evening and morning. These weevils can fly but do so rarely as they are sedentary. The newly emerged adults feed on bark of new stem shoots. They mate and can lay eggs shortly after emergence (2 to 10 days). Eggs are laid in crevices of the bark. Females can also chew into the bark, making round holes in which they oviposit one or several eggs and pack with bits of wet sawdust-like wood. There are two peak egg-laying periods: the first in March and April by overwintering adults; and later in July through October from the newly emerged adults (Solomon, 1995)(Garbutt and Harris, 1994). Adults can live two to three years (Garbutt and Harris, 1994). The adult weevils can make a stridulating sound when handled.
Larvae move from overwintering tunnels between the bark and wood, deeper into the stem often into the pith. Pupation occurs in frass plugged galleries, usually from mid-July through September and lasts two to three weeks.
Tree damage includes frass-plugged entrance holes; bark cracking and weeping; round exit holes (often sawdust at base of plant), galling of trunks, larval tunneling which girdles the trees, tree breakage, and secondary pathogens infecting borer wounds. Attacks are most common in stems 2.5 to 10.0 cm in diameter (Solomon, 1995). Galleries are round and often packed with frass.
Solomon, J.D. 1995. Guide to insect borers in North American broadleaf trees and shrubs. Agric. Handbk 706. Washington, DC: U.S. Department of Agriculture, Forest Service. 735 p.
Poplar and willow borer. 1994. Garbutt, R.W.; Harris, J.W.E. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Forest Pest Leaflet 07, Copublished by the BC Ministry of Forests.
BC Ministry of Forests:
and willow borer, Cryptorhynchus lapathi Nice
Poplar and willow borer tunneling in pith (cross
section) (tentative ID)