Black vine weevil

What is black vine weevil?

Black vine weevil is a snout beetle from Europe. Every adult in North America is female, and none can fly. They walk to host plants at night, chew notches in the leaf edges, and hide in mulch, leaf litter and dense foliage during the day.

The leaf notching rarely hurts the plant. The grubs are the real problem. They live in the soil, feed on fine roots through summer and fall, and in early spring chew the bark of larger roots and stems, sometimes girdling the plant. Penn State notes root damage often goes unseen on container plants and those plants often die after they are set out in the landscape.

Yew is the favorite host, which is why it is also called the taxus weevil, but rhododendron, azalea, hemlock, euonymus and Japanese holly are common targets too, along with perennials like hosta and heuchera.

Signs and damage

• Half-moon notches chewed in leaf edges
• Yellowing, wilting or dying shrubs from root damage, often after planting
• Bark chewed off large roots or the base of the stem, sometimes girdling the plant
• White, legless, C-shaped grubs with brown heads in the root zone
• Black, snouted beetles that drop to the ground when disturbed (seen at night)

Black vine weevil identification: what to look for

• Adult: Slate gray to blackish brown, about 3/8 to 1/2 inch (9 to 13 mm), short snout, elbowed antennae, bumpy wing covers with tiny patches of golden hairs. Flightless; all females. Adults can live 90 to 100 days.
• Larva: White, legless, C-shaped grub with a brown head, up to about 1/2 to 5/8 inch.
• Eggs: Up to 500 per female, laid in soil near the base of host plants.
• Damage: Adults: half-moon notches in leaf edges. Grubs: eaten roots, chewed root and stem bark, girdling, plant decline.
• Timing: In PA, adults emerge late May through June and feed about three to four weeks before laying eggs.

Life cycle

One generation a year. Grubs spend the winter in the soil and pupate there in early spring. Adults come out from late May through June, feed on leaves at night for 21 to 28 days, and then lay up to 500 eggs each in the soil near plant bases over a few weeks. Eggs hatch in 10 to 14 days and the grubs feed on roots until fall and spend the winter in the soil. Some adults survive winter inside homes.

When to look: Look for leaf notches starting in June. Penn State suggests placing boards or loose burlap on the mulch under host plants in early May and checking them at midday to find the first adults. Adults feed at night, so check plants after dark.

Black vine weevil look-alikes

A few things get mixed up with it:

• Strawberry root weevil (Otiorhynchus ovatus): UW-Madison calls it a close relative; it is also a root weevil whose larvae feed on roots.

How to control black vine weevil

Cultural control

• Clean up leaf litter, plant debris and dropped branches in beds to remove hiding places.
• Monitor with boards or loose burlap on the mulch under host plants from early May, turning them over at midday (Penn State).
• At night, knock adults onto a white sheet and destroy them (slow, and some will be missed).
• Container plants can hide root damage (Penn State), so check root balls before planting.
• Some rhododendrons resist leaf feeding.

Biological control

• Beneficial (entomopathogenic) nematodes applied as a soil drench attack the grubs; NC State names Heterorhabditis bacteriophora as fairly effective. UMass says they work best in containers and when soil temperature suits the nematode; water before and after applying.
• Birds eat some weevils.

Chemical control

Adults: Penn State says to apply a registered insecticide to host leaves about three weeks after the first adult is found and again three weeks later, because adults keep emerging; NC State cites Ohio State timing of mid-June, when roses bloom, with three sprays at three-week intervals. UW-Madison says to treat after adults emerge but before eggs are laid, in late afternoon or early evening since adults feed at night. NC State says some pyrethroids are effective when adults are present but warns not to use pyrethroids around pools, ponds and streams, and reports carbaryl and malathion as not effective. Grubs: harder to reach; NC State names imidacloprid as a soil drench or injection, and UW-Madison notes many products bind to mulch and organic matter and never reach the grubs. Apply after bloom and when pollinators are least active. Use only products labeled for this use; the label is the law. Pesticide work for hire needs a licensed applicator; see our pesticide applicator license guide. Muthler Landscaping does not spray or apply pesticides.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Check root balls of yew, rhododendron and other hosts for C-shaped grubs before planting.
• Keep beds free of excess litter and debris where adults hide.

When to call a pro

Call a licensed pesticide applicator if yews or rhododendrons are declining from root feeding or notching is heavy year after year. Your Penn State Extension county office can help confirm grubs.

Related guides: Tree database: mature size and planting distance · Pennsylvania tree identification · Firewood rules by state · All pests and diseases

Questions about black vine weevil

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