Black Vine Weevil
Attacks:
Yews, rhododendron, arborvitae
What you will see:
- Adults notch leaves and flowers
- Larvae feed on roots and can kill plants
Life cycle:
- Overwinter as larvae
- Adults emerge from June to July
- After feeding for 2-3 weeks, adults begin to lay eggs
- Adults active through September
- Eggs are laid on the ground in leaf litter
- Larvae feed until they overwinterAdults may also overwinterOne generation per year
- All weevils are females (no males exist)
Treatment and Applications:
- Insecticides (60% effective):
- Soil drench for overwintering larvae
- Foliage spray for adults 2-3 sprays
Cultural practices:
- Expose eggs to desiccation and predation
- Reduce soil moisture
- Remove organic matter from base of plants
- Create mechanical barriers to prevent infestation
- Weevils cannot fly, will fall into pits
- Barriers are only effective as a preventative measure
Biological control:
- Parasitic Nematodes: Make sure nematodes are alive prior to treatment
- Saturate soils before and after treatment
- Very effective in container plants
- 50/50 or less effectiveness in landscapes
Additional Black Vine Weevil Information:
A harmful pest commonly found in plant and landscaping nurseries is the black vine weevil. A native of Europe, this species showed up in Connecticut in 1910. The pest is one of the most widely destructive and distributed species of root weevils. Adults and larvae opt for Japanese holly and similar plant species. They feed on the roots of hemlock, Tsuga spp. This pest has shown up in more than 100 species of cultivated and wild plants. Pest managers often refer to this insect as the taxus weevil.
In its larval stage, the pest is white, legless, and shaped like a C and has a brown head. Adults are slate gray to black. They don’t fly, and are about 9-13 mm long, they have a short-pronounced snout with elbowed antennae. The front wings are covered with tiny concave areas and small patches. The strawberry root weevil looks like this species but is only half the size of the black vine.
This pest overwinters as immature larvae in the soil. The mature larvae are up to 10-15 mm long and create resting cells in the soil in spring. Adults emerge in late May to June, in North America only females emerge. As active night feeders, the adults drop quickly if they are disturbed. During the day, adults hide in dark places of stems or dense foliage or leaf litter and mulch.
The larval stage of these pests is highly destructive to the plants. Feeding larvae emerge in mid-summer through early spring, and then move to the bark of large roots or the stem, sometimes girdling them. Damaged roots can go undetected in container-grown plants or nurseries, but the infested plants in landscapes frequently die. Injury caused by adults, such as notching, is minimal and does not impact the plant health.