Black Vine Weevil

What it does

Adults feed at night, chewing distinctive C-shaped notches along the margins of leaves; by day they hide in mulch, soil, and debris. Adult leaf notching is mostly cosmetic, but the legless grubs feed on roots and can girdle the crown, wilting or killing rhododendrons, azaleas, and especially potted or nursery plants. Flightless adults sometimes wander indoors.

Where it lives

The black vine weevil is common in cooler regions, including the Pacific Northwest, Northeast, and northern states, on broadleaf evergreens and many ornamentals in landscapes, gardens, and nurseries. Grubs live in the root zone and potting media, while adults shelter in mulch and ground litter around host plants.

How it breeds

In the US the black vine weevil is parthenogenetic, so all adults are female and lay eggs without mating. Eggs are laid in the soil in summer; grubs feed on roots through fall, overwinter, and pupate in spring, with new adults emerging in early summer. There is generally one generation per year.

What it eats

Adults chew the leaf margins of rhododendron, azalea, yew, hemlock, euonymus, and many other ornamentals and small fruits. The grubs feed on the roots and crowns of the same plants, favoring container and nursery stock.

Identification

Adults are about 10 mm, dull black, pear-shaped, and flecked with tiny patches of yellowish hairs, with a short broad snout and elbowed antennae; they cannot fly. Grubs are white, legless, C-shaped, and found in the root ball. Nighttime leaf notching plus wilting rhododendrons points strongly to this weevil.

Signs of an infestation

• C-shaped notches chewed along leaf margins, appearing overnight
• Wilting or declining rhododendrons, azaleas, or potted plants
• White, legless, C-shaped grubs in the root zone or potting media
• Dull black flightless weevils in mulch or wandering indoors
• Girdled stems or roots on container and nursery plants

Prevention tips

• Inspect for notched leaves and check root balls of declining plants
• Handpick adults at night when they feed
• Reduce mulch and debris that shelter adults near valued shrubs
• Use sticky barriers on stems or pots to trap climbing adults
• Consider beneficial nematodes in moist soil to attack grubs

Professional solutions

Root-feeding grubs are the harder problem; gardeners can apply beneficial nematodes to moist soil and target adults at night. For repeated ornamental losses or nursery stock, professional help or your Cooperative Extension office can advise on soil-applied products, nematode timing, and confirming the weevil versus other causes of shrub decline.