Vine Weevil

Nematodes for larvae + monitoring adults.

Adult vine weevils cause leaf notching; larvae destroy roots…

About Vine Weevils

Vine weevils (Otiorhynchus sulcatus) are one of the most destructive pests affecting UK ornamental and soft-fruit production. While adults cause cosmetic leaf notching, the true damage comes from the soil-dwelling larvae, which feed aggressively on roots, collars and lower stems. Severe infestations cause plant collapse, wilting, poor establishment and sudden crop loss.

Symptoms of Vine Weevil Damage

• Distinctive “U-shaped” notches on leaf edges (caused by adults)
• Plants wilting despite moist substrate
• Poor rooting, stunting and slow establishment
• Roots stripped clean by larvae
• Sudden collapse in severe larval infestations
• Presence of creamy-white C-shaped larvae in compost

Why Biological Control Works

Biological control is the industry standard for vine weevil management because larvae remain hidden in the compost, where chemical sprays are ineffective. Entomopathogenic nematodes such as Steinernema kraussei and Heterorhabditis bacteriophora actively seek out larvae and infect them, providing reliable control when soil temperatures are within the correct range.

Key UK Vine Weevil Biology

• Adults are flightless and emerge mainly from April to September
• Females lay up to 1,000 eggs in soil around plant bases
• Larvae cause the majority of crop damage
• Pest overwinters as larvae and pupae in pots or ground beds
• Preferred hosts include heuchera, strawberries, camellia, primula and many ornamentals

IPM Recommendations

• Apply nematodes preventatively during egg-laying months
• Monitor adult activity with corrugated traps and nighttime inspections
• Use physical barriers (e.g. copper tape) on pots where appropriate
• Keep compost evenly moist to support nematode activity
• Avoid over-potting or waterlogged media, which increases larval success

Preventative vs Curative Strategy

Preventative:

• Apply Steinernema kraussei in early spring when soil temperatures are as low as 5°C. Ideal for ornamentals and hardy nursery stock.
• Repeat applications during peak egg-laying (late spring to early autumn) to target early-stage larvae.

Curative:

• Use Heterorhabditis bacteriophora in warm conditions (12°C+), including late summer hotspots where larvae are larger.
• For crops showing collapse or heavy larval presence, drench with a curative nematode rate.

Environmental Notes

• S. kraussei is the only nematode effective at very low temperatures (5–12°C)
• H. bacteriophora performs best at 12–20°C
• Nematodes require moist compost — avoid letting pots dry out after application
• Avoid fungicides or drenches that harm beneficial nematodes