How Can I Control Black Vine Weevils?

Do you want to control black vine weevils using the biological control method?

Do you want to control black vine weevils using low-risk (organic) insecticides?

Do you want to control black vine weevils using traps?

Do you want to control black vine weevils using insecticides?

Parasitic (entomopathogenic) nematodes can be drenched onto the soil beneath infested plants to reduce larval abundance if the soil is well-drained and not compacted. Apply nematodes when weevil larvae are expected to be present in midsummer to fall. During hot weather, apply nematodes in the early morning or evening. The soil must be warm (at least 60°F) and moist (well-irrigated) but not soggy before applying nematodes and for 2 weeks after application. If warranted, irrigate every 2 to 3 days after applying nematodes to soil.

A highly effective biological insecticide containing Beauveria bassiana, an entomopathogenic fungus that attacks a long-list of troublesome pests can be used to control black vine weevils. Weekly applications can prevent insect population explosions and provide protection equal to or better than conventional chemical pesticides. Diatomaceous earth can be used for long-lasting pest protection. Made up of tiny fossilized aquatic organisms, diatomaceous earth kills by scoring an insect’s outer layer as it crawls over the fine powder.

One traping strategy is to wrap trunks overnight with burlap or corrugated cardboard, then during the day remove and inspect wraps and dispose of any weevils that sought shelter there. Pitfall traps such as cups buried in soil near the base of plants can also be used. Trim branches that provide a bridge to other plants or the ground and apply a 6-inch band of sticky material to trunks to prevent the flightless beetles from climbing trunks to feed on foliage. First, wrap the trunk several inches wide with landscape fabric or plastic, then apply the sticky material on top of the wrap. Periodically replace wraps to prevent growth-restriction damage to trunks.

During spring, about 1 week after adult chewing is first observed, spinosad can be sprayed on leaves in the evening. Because of its short persistence, repeated application 7 to 10 days later may be needed. If plants are especially susceptible to damage, a more persistent insecticide (e.g., carbaryl) can be applied. If weevil emergence is prolonged and new leaf chewing continues to appear, a second foliar spray may be made about 3 to 4 weeks after the first application. Applying a systemic insecticide such as imidacloprid to soil or trunks can control both adults and larvae.

Handpick and destroy adults beginning in spring to reduce the later abundance of larvae and their feeding damage. For example, where leaf notching is observed, after nightfall shake or branch beat plant parts over a sheet or other collecting surface; gather and crush or dispose of any dislodged weevils. Remove mulch and other hiding places from around plants and water only when necessary.