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The P&PDL Picture of the Week
for 15 December 2003



White Pine Weevils

Cliff Sadof, Department of Entomology, Purdue University

White pine weevils are becoming an increasing problem in Indiana landscapes. Figure 1 shows how the top of a mugho pine can be killed after weevil larvae tunnel into stems. Figure 2 shows the holes left in the stems after adult weevils have left the shoots. These weevils are known to attack all species of pines, Norway spruce and Colorado blue spruce.

Adults winter in leaf litter and fly to tree tops to mate when the weather warms in the spring. Females lay many eggs in terminals that hatch into grubs that bore into shoots. Legless larvae continue to feed until July when they pupate in chip bark cocoons. Adults emerge in August and chew on twigs.

In early spring (April) applications of broad spectrum insecticide to tree tops should be timed to kill adults gathering on twigs. Prune and destroy damaged leaders that contain larvae or chip bark cocoons before adults emerge in August. Mixed species plantings of pines are less likely to build damaging numbers of this pest than pure stands of susceptible species.

Click on the small image to view a larger image.

Figure 1. Top of a mugho pine
after weevil larvae tunnel into stems

Figure 2. Holes left in the stems
after adult weevils have
left the shoots

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Last updated: 15 December 2003/amd
The Plant & Pest Diagnostic Laboratory at Purdue University