Pest
Vine weevil
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in March | Watch for in April | Watch for in May | Watch for in June | Watch for in July | Watch for in August | Watch for in September | Watch for in October |
What it is
Vine weevil is a dull black beetle about 9 mm long, with faint yellowish speckles and a short snout. Every adult in Britain is female, and each can lay many hundreds of eggs without mating. The adults are a cosmetic nuisance, but their larvae are one of the most destructive pests of plants in pots.
Symptoms
Adults chew irregular U-shaped notches from leaf margins, typically on rhododendrons, camellias and euonymus. Underground, plump, cream, C-shaped grubs with brown heads eat roots and can hollow out corms, tubers and the base of stems. Infested pot plants suddenly wilt in autumn or spring even though the compost is moist, and they may lift out of the pot with no roots at all.
Cause
Adults emerge from late spring, hide by day and feed at night. Eggs are laid in the soil or compost from summer to autumn, and the grubs feed through autumn, winter and early spring before pupating. Peat-free and soilless compost in containers suits them well, which is why pots suffer most.
Control
Search plants by torchlight on mild nights and pick off adults, or shake shrubs over a sheet. Lay corrugated card or a board beneath pots as a hiding place and check it regularly. When repotting, tip out the compost and destroy any grubs. A drench of the parasitic nematode Steinernema kraussei kills grubs when compost is above about 5°C; apply in late summer and again in early autumn. Chemical drenches are a last resort for ornamental pots only; follow the label.
Prevention
Inspect the root balls of new plants before buying or planting. Use a gritty top dressing on pots, which deters egg laying. Encourage frogs, toads, ground beetles and birds, all of which eat weevils. Keep greenhouse benches tidy so adults have fewer places to hide.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: March, April, May, June, July, August, September and October.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.