Many people who grow rhododendrons often notice that the leaves of their plants exhibit notches. This is the work of the black vine weevil, Otiorhynchus sulcatus (F.) and to a lesser degree, the strawberry root weevil, O. ovatus (L.).
These weevils feed on the foliage of a variety of broadleaved evergreens, hemlock, taxus, and other ornamentals. They are nocturnal feeders and hide in and around the plant during the day. If disturbed, they will fall to the ground to escape as they are unable to fly.
While the adult feeding is unattractive and disturbing it is the larval feeding that actually damages the plant the most. Black vine weevil larvae feed on the roots of the host plants, weakening and sometimes killing them, especially after transplanting. Ornamentals can also be killed if the larvae girdle the stem.
Life Cycle
There is one generation a year with the snout nosed, 1/2-inch adult weevils emerging in mid- to late-June. They feed for one or two weeks after which they begin laying eggs. All of the adults are female and each can lay up to 500 eggs. Each egg is deposited near the base of the host plant. In 10 days to 2 weeks, the 1/2-inch pink grubs hatch and tunnel into the soil to reach the roots. The most extensive larvae feeding occurs in late-May and early-June, just prior to pupation.
