WHITE PINE WEEVIL ( Pissodes strobi )
The White Pine Weevil, is a major source of concern to Christmas tree growers. Although the weevil rarely kills an entire tree, it usually kills the terminal shoot and top one or two whorls of branches. Eastern white pine and Norway spruce appear to be two of its preferred hosts, although other pine and spruce, and Douglas-fir, are also suceptible. White pine weevils overwinter as adults in litter beneath host trees. This one of the earliest pests to become active in the spring, requiring just 7-58 GDD before emerging from the litter. The first signs of weevil ovipositing may appear as early as mid-April.
Shortly after mating the females chew small holes in the bark and then lay between one and five eggs there, covering them with macerated bark. Sap flow from this wound, along with a slight swelling of that part of the leader, are usually good signs that the female has laid her eggs in a particular site. Eggs hatch and larvae feed and develop within the shoot. Infested leaders will begin to droop and die beginning about mid-June producing the characteristic shepherd's crooks that are often associated with white pine weevil injury. Larvae pupate in the shoots in chambers filled with shredded wood and bark, and the adults emerge in late summer or early fall to feed. Each adult is about 1/4 inch long with a light brown body and the prominant hooked snout that is typical of all weevils.
The best time to treat this pest is in the spring when the adult females are laying eggs. Once egg laying is complete, the leader will most likely be killed by larval acivity. A registered insecticide may be used to control this pest. Treat once in the early spring just as buds break to catch the overwintering adults as they emerge to feed on the shoots. Cut out dead leaders and destroy them by the end of June to control larvae. Natural enemies do not provide adequate control.
Fig. 1. Here you can see an adult female white pine weevil. The sap flow is from holes where the weevil has deposited eggs.
Fig. 2. Shepherd's crook on spruce, characteristic of white pine weevil injury
Fig. 3. Terminal whorl of white pine, killed by white pine weevil
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