Black Wine Weevils

The black vine weevil, Otiorhynchus sulcatus, is a small, dark beetle with a short snout that is a well-known pest of gardens, nurseries and potted plants. It is sometimes misspelled “black wine weevil,” but its name refers to vines such as grapevines, which it can also attack.

Black vine weevil Quick Facts

Common name	Black vine weevil
Scientific name	Otiorhynchus sulcatus
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Coleoptera
Family	Curculionidae
Genus	Otiorhynchus
Type	Insect (weevil)
Diet	Adults eat leaves; larvae eat roots
Habitat	Gardens, nurseries, greenhouses and potted plants
Native range	Europe; now widespread in North America and elsewhere
Size	Adults about 8-11 mm; larvae about 10-12 mm
Colours	Dull black with small golden hair patches
Special feature	Cannot fly and almost all are female

Weevils are a big family of beetles with snouts. The black vine weevil is native to Europe but has spread to North America and many other parts of the world, probably carried in the soil of potted plants.

What It Looks Like

Adult black vine weevils are about 8 to 11 mm long, roughly 3/8 of an inch. They are dull black or dark gray, with small patches of golden or yellowish hairs on their wing covers. They have a short, broad snout and elbowed antennae.

Their wing covers are joined together, so black vine weevils cannot fly. They get around by walking, which is why they often stay on the same plant or move slowly through a garden.

The larvae are legless, C-shaped grubs that are creamy white with a brown head. They grow to about 10 to 12 mm long and live in the soil around plant roots.

Host Plants

Black vine weevils eat more than a hundred kinds of plants. Some favorites are:

• Rhododendrons and azaleas
• Yews and hemlock
• Euonymus, Japanese holly and camellia
• Hostas, heucheras, astilbes, sedums, lilies, phlox and asters
• Strawberries, grapevines, cyclamen, primroses and many other potted plants

Behavior and Diet

Adult black vine weevils feed at night. During the day they hide in mulch, leaf litter, soil cracks and garden debris. At night they climb up plants and chew on the edges of leaves, leaving neat crescent-shaped notches.

The larvae feed underground on roots. Young larvae nibble the small, fine roots. As they get bigger, they feed on larger roots and may chew the bark off the base of the stem, which is called girdling.

Life Cycle

Almost all black vine weevils are female. Males are extremely rare or unknown, so the females lay eggs that develop without mating. This means a single weevil can start a whole new population.

New adults appear in late spring or early summer. Each one must feed on leaves for about three to four weeks before she starts to lay eggs. Over the summer, she lays hundreds of tiny eggs in the soil near the base of plants. The eggs hatch in about two to three weeks.

The larvae feed on roots through late summer and autumn. Most spend the winter as larvae in the soil, moving deeper when it gets cold. In spring, they feed a little more, then turn into pupae in small chambers in the soil. New adults come out a few weeks later. In most places there is one generation a year.

Damage

The larvae do the most damage. By eating roots and girdling the stem, they stop water and nutrients from reaching the rest of the plant. Infested plants may wilt, turn yellow, stop growing and eventually die. Often the first sign is a plant that suddenly collapses, even though it has been watered.

Plants in containers, greenhouses and nurseries are at greatest risk, because the larvae are hidden inside the pot and the warm conditions help them. Adult leaf notching looks untidy, but it rarely harms a plant’s health on its own.

How to Manage Black Vine Weevils

Gardeners have several safe ways to control black vine weevils without strong chemicals:

• Hunt at night. With an adult’s help, go out with a flashlight after dark and pick weevils off plants, or shake plants over a white sheet or tray.
• Set simple traps. Place a small board or a piece of burlap under affected plants. Weevils hide underneath during the day, so you can check and remove them each morning.
• Use beneficial nematodes. These microscopic worms are watered into the soil, where they find and kill weevil larvae. They work best in late summer or autumn, when the soil is moist and warm enough.
• Check new plants. Tip potted plants out of their pots and look for white grubs among the roots before planting them.
• Use barriers. Sticky bands or grease around the rim of pots can stop the flightless adults from climbing in.
• Keep the garden tidy. Clear away plant debris where adults hide during the day.

Insecticides should only be a last resort and must be used by an adult, exactly as the label says, and kept well away from children, pets and wildlife. Local garden or extension services can give advice on what is safe and allowed in your area.

Black vine weevil FAQs