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
Figure 2. Holes left in the stems
after adult weevils have
left the shoots
Back to top of page | Past Pictures of the Week Index