Black Vine Weevil

The black vine weevil is a flightless beetle in the weevil family (Curculionidae), order Coleoptera, best known as a pest of ornamental shrubs, strawberries, and container-grown nursery stock. Adults in most populations are all female, reproducing by parthenogenesis without the need for males, which lets a single individual establish an infestation. It is active almost entirely at night, hiding by day in mulch, soil cracks, or under leaf litter.

Its larvae live below ground and chew on plant roots and crowns, while adults are foliage feeders that leave characteristic notches along leaf margins. This split lifestyle—root-feeding grub, leaf-feeding adult—means the insect can be present and damaging at two different life stages, in two different places on the plant, at different times of year.

Because it has been spread widely through the nursery trade, the black vine weevil now occurs across much of the Northern Hemisphere and in some temperate regions of the Southern Hemisphere, making it one of the more cosmopolitan weevils encountered in home gardens and commercial greenhouses alike.

• Adult: 8–14 mm long, dull black to charcoal-gray body covered in fine, short golden-brown hairs and small scale-like flecks on the wing covers, giving a slightly mottled look.
• A short, broad snout typical of weevils, with elbowed antennae tipped in small clubs.
• Elytra are fused and roughened with rows of pits; the hind wings underneath are non-functional, so this weevil cannot fly.
• Legs are relatively long and spiny, useful for climbing plant stems at night.
• Lookalikes: other Otiorhynchus weevils look nearly identical and are best told apart by host plant and range; the strawberry root weevil is smaller and more oval.

Found in gardens, nurseries, greenhouses, and landscaped beds wherever host shrubs such as yew, rhododendron, azalea, hemlock, and strawberry are grown. Adults hide during the day in soil, mulch, or leaf litter near the base of host plants and climb up to feed after dark, especially in spring and summer. Larvae remain in the soil profile close to plant roots and crowns year-round.

Adults are nocturnal leaf-notchers, chewing crescent-shaped notches from leaf margins without eating through major veins; being flightless, they disperse mainly by walking or through the movement of infested nursery stock and soil. Larvae are subterranean and feed on fine roots, then progress to girdling larger roots and crowns as they grow, which is the more consequential stage of the insect's life cycle for the plant. Populations are typically all-female, reproducing without mating. The species overwinters as larvae in the soil.

Complete metamorphosis (egg, larva, pupa, adult). Adults emerge in late spring to early summer, feed for several weeks, then lay eggs in the soil near host plants; a single female can lay hundreds of eggs over her lifetime. Eggs hatch into small, legless, C-shaped white grubs with tan heads that feed on roots through summer and fall, then move deeper into the soil to overwinter as larvae. Pupation occurs in the soil the following spring, with new adults emerging in late spring—one generation per year in most climates.