Identification and Control Methods of the Red Pine Pest Red Wood Borer Weevil

Why is the red wood borer weevil considered an important pest of young red pine trees?

Because the larvae of the red wood borer weevil bore under the bark of red pine branches and shoots, causing the main shoot and side shoots to be damaged and die. This not only affects the growth of red pine, but can also cause the branches and trunk to crack and exude resin, weakening the tree's vigor and allowing other pests and diseases to invade and cause harm. Moreover, because this insect spends most of its life cycle under the bark of branches, it is difficult to control. Once it occurs in a forest, it may bring serious consequences of forest destruction.

How to identify the red wood borer weevil?

The adult of this insect is a small beetle, belonging to the weevil group. The body is dark brown, 8-9 mm long and 3-4 mm wide. There is a nose-like projection extending from the front of the head, which is the pest's mouthparts. There is 1 pair of round white spots on the back and 1 pair on the front end of the forewings, and an "X"-shaped white band at the rear end of the forewings. The egg is oval, 1 mm long, milky white. The mature larva is 6-8 mm long, milky white. The head is pale yellow, and the tail has 4 yellow bristles; the head and tail curve toward the abdomen. The pupa is 7-8 mm long, milky white, with pale yellow compound eyes and 4 yellow bristles at the tail.

How to understand the occurrence pattern of the red wood borer weevil?

This insect has 1 generation per year (a). In early October, the larvae successively overwinter in the tunnels in the phloem of the trunk. In late April of the following year, they begin activity, pupate in late May, adults first appear in late June, and mating and egg-laying occur in early to mid-August. After emergence, adults need to feed on red pine shoots before they can lay eggs. Adults have a death-feigning habit and weak flying ability. After mating, the female chews a small hole in the branch or trunk and lays eggs inside the hole. After hatching, the larvae enter under the bark to cause damage, mostly feeding from bottom to top, and the frass and excrement produced by boring remain in the tunnels. Within 1 year (a), the larvae have 2 damage periods, the 1st before June and the 2nd from September to October.

This insect mostly occurs in 10-30-year-old red pine plantations; red pine under 10 years old usually is not affected. Trees growing on sunny slopes are more severely damaged than those on shady slopes, sparse woodlands more severely than dense woodlands, and forest edges more severely than the forest interior.

How to control the red wood borer weevil?

Advocate afforestation under the forest canopy. Try to avoid afforestation on clear-cut sites. Avoid establishing pure red pine forests.

Strengthen silvicultural measures and promptly remove severely damaged trees. Convert pure forests into mixed coniferous-broadleaf forests.

During the adult stage, spray 40% dimethoate emulsifiable concentrate at 250 times dilution or 50% fenitrothion emulsifiable concentrate at 500 times dilution to control adults.