Poplar-and-willow borer

Latin name: Cryptorhynchus lapathi (Linnaeus).
French name: Charançon du saule
Order: Coleoptera
Family: Curculionidae

Description

Distribution

Quebec, Newfoundland, Ontario, British Columbia

Micro-habitat(s)

Trunk, Twig, Annual shoot, Litter, Bark, Base of tree

Damage, symptoms and biology

There are a number of wood boring insects commonly found in live hardwoods. Most notable of these are the carpenterworm (Prionoxystus robiniae [Peck]), the poplar carpenterworm (Acossus centerensis [Lint.]), the aspen carpenterworm (A. populi [Wlk.]), the ash borer (Podosesia syringae [Harr.]), the cottonwood crown borer (Sesia tibialis [Harr.]), and the poplar-and-willow borer (Cryptorhynchus Iapathi [L.]). There are many other wood boring insects, most of which are bark beetles (Scolytidae), flatheaded wood borers (Buprestidae), and roundheaded or longhorned beetles (Cerambycidae). Most of the latter borers attack only dead or dying trees and are not usually a problem in living trees that are healthy.

These wood boring insects often go unnoticed in the trees they are attacking until severe damage has resulted. When attacked by one or more of these borer species, trees are usually weakened structurally and are susceptible to wind and snow breakage, especially if they are repeatedly attacked. Severe attack can place trees under stress, making them more susceptible to other damage agents such as drought and disease. If a tree is suspected of being attacked by a wood boring insect, careful examination will reveal small entry holes in the bark (often in and around old wounds) where the larvae of the developing moths or beetles extrude frass or debris. In many cases, small amounts of sap bleed from these entry holes. When a tree is severely attacked, large amounts of frass will accumulate at the base of the tree. Splitting the branches or stem of an attacked tree will reveal wood that is riddled with feeding tunnels.

The poplar-and-willow borer requires 2 years to complete its life cycle in the Prairie Provinces, and the adult borer is capable of surviving a third winter. Larvae pupate within wood chip-filled chambers of attacked shoots. Both male and female adults are rough-surfaced, snout-nosed beetles, about 8- to 10-mm long. They are mostly black except for the hind third of their hardened wings (elytra), which are initially gray-pink but turn light brown. These borers have functional wings but rarely fly. Adults feed on many young succulent shoots before mating. Oviposition takes place in the summer when females make small punctures in the shoots and deposit a single egg (sometimes as many as three) in each puncture. Once the eggs have hatched, the larvae feed at first by mining the bark and then later move into the wood. Larvae are creamy-white, C-shaped grubs and have a full-grown length of 13 mm.

Other information

A number of biotic agents act as natural controls for wood borers of hardwoods. Studies have shown that birds, particularly woodpeckers, may feed on up to 75% of a population of wood borers and are probably the most effective natural control agent. Parasitic insects, especially parasitic wasps, also feed on wood borers. In the United States, fast-growing wood decay fungi have been documented as trapping pupae within feeding tunnels, thus preventing adult emergence.

Most of the wood borers prefer wounds and scars on trees for oviposition. Care should, therefore, be taken when working on or near ornamental hardwoods, because careless cultivation, pruning, or mowing may cause injury resulting in oviposition sites. Ornamental trees that are healthy and growing well are most resistant to wood borer attacks. During drought, trees should be watered to prevent the drought stress that may predispose trees to wood borer attacks.

If a high-value ornamental tree has been attacked by only a few larvae, these larvae may be killed by inserting a flexible, small gauge wire into the entry holes. When the wire is fully inserted it may puncture and kill the burrowing larva. Several attempts may be necessary to be successful. When trees have been severely attacked (i.e., brood trees), they should be removed and destroyed before neighbouring trees can be attacked by subsequent generations emerging from the brood trees.

Canadian Forest Service Publications

Poplar-and-willow borer

Diet and feeding behaviour

Phloeophagous : Feeds on phloem.
- Borer: Bores into and feeds on the woody and non-woody portions of plants.
Xylophagous : Feeds on woody tissues (wood).
- Borer: Bores into and feeds on the woody and non-woody portions of plants.

Information on host(s)