Black vine weevil
A flightless, dull black snout beetle 3/8–1/2 inch (9–13 mm) long. The adults feed at night and cut half-moon notches in leaf edges, which looks bad but rarely harms the plant. The damage that matters is done by the grubs: plump, white, legless and C-shaped, they live in the soil or compost and eat the roots. Rhododendron, azalea, yew, strawberry and almost anything in a container are at risk, and an infested pot plant often wilts and dies between autumn and spring. The standard control is insect-killing nematodes watered into moist, warm compost.
Adult Otiorhynchus sulcatus on a rhododendron leaf with marginal notching. Photo: pending.
Identification
Adults are 3/8–1/2 inch long (9–13 mm), slate grey to dull black, pear-shaped from above, with a short, broad snout and elbowed antennae. The wing cases are pitted and carry small patches of golden hairs or pale scales. They cannot fly, but they climb well. By day they hide in leaf litter, under pots or under benches, and they come out to feed after dark. Every adult is female: they reproduce without mating.
The grubs are the stage you actually find. They are plump, white and legless with a light brown head, curl into a C, and grow to about 3/8–5/8 inch (10–15 mm): the RHS gives 10 mm, UC IPM about 1/2 inch and Penn State 10–15 mm. They sit among the roots. The tiny brown eggs are almost invisible in compost, and the larger yellow-brown balls often seen in nursery pots are slow-release fertiliser pellets. The strawberry root weevil (O. ovatus) looks similar at about half the size.
Easily confused with
- Strawberry root weevilAlso a pestA close relative (Otiorhynchus ovatus) that looks much the same but is about half the size of a black vine weevil.
- White grubsAlso a pestAlso C-shaped and white with a brown head, but they have three pairs of legs. Vine weevil grubs are legless.
- Slow-release fertiliser pelletsHarmlessThe yellow-brown balls in nursery compost are fertiliser, not eggs. Vine weevil eggs are tiny, under 1 mm, brown and almost invisible.
Damage symptoms
Adult feeding is obvious and mostly harmless. Penn State notes it seldom affects plant health even when extensive, and the RHS advises tolerating it. The grubs are what kill plants. They eat fine roots in autumn and larger roots in spring, gnaw the bark off the bigger roots and stem bases, and can girdle a shrub below the soil line. In containers the damage goes unseen until the plant collapses. The RHS finds most losses between September and March, as the grubs finish growing.
- Half-moon notches in the leaf edges, especially on thick-leaved evergreens such as rhododendron
- Pot plants wilting in moist compost, often between autumn and spring
- Plants that lift out of the pot or ground with most of the roots gone
- Tunnels in cyclamen and begonia tubers, or in the stem bases of cacti and succulents
- Yellowing leaves, stunting or plant death on rhododendron, azalea and yew
- White C-shaped grubs with brown heads among the roots
Lifecycle & degree days
Outdoors in North America there is one generation a year. The winter is spent as part-grown grubs in the soil, which feed again in spring, then pupate in late May and June. Adults emerge from June into July (about 600 degree days °F in Massachusetts) and feed for two to four weeks before they start laying (UMass says two to three, Penn State 21–28 days). Egg-laying runs from late July (about 1,400 degree days), and the new grubs hatch from August (about 1,700). Each female can lay up to 500 eggs, and she needs no male to do it. The degree-day figures are UMass's for its landscape plants; timing elsewhere will differ.
- Generations / yr
- 1 outdoors
- Adults emerge
- Late May–July; ~600 degree days °F (UMass)
- Eggs
- Up to 500 per female, after 2–4 weeks of feeding
- Overwinters
- Part-grown grubs in the soil
Host crops
Recorded on more than 100 cultivated and wild plants. Penn State lists rhododendron, yew, euonymus and Japanese holly as the preferred hosts, and UC IPM adds azalea, caneberries, grape, liquidambar and strawberry. The RHS finds that plants in containers, outdoors or under cover, are by far the most likely to be killed. In open ground, heavy grub numbers mainly build up on strawberries, primula, sedum, heuchera and young yew.
Monitoring & action thresholds
No extension source gives a numeric threshold. Notched leaves show that adults are about, and they tell you when to act. In containers, act as soon as you find grubs among the roots or a plant wilts in moist compost. The RHS advises tolerating the adult leaf damage itself.
Look for fresh notches on rhododendron and other thick evergreen leaves from late spring. From early May, Penn State suggests laying 6 × 6-inch boards on the mulch under host plants, and UMass suggests a pleated burlap square around the base. Check underneath for sheltering adults; Penn State says daily until the first appear, UMass weekly from mid-June to August. On mild evenings, a torch will pick out the adults feeding. In pots, knock out any plant that wilts in moist compost and look among the roots.
Biological control
Insect-killing nematodes are the main biological control. UC IPM advises drenching Heterorhabditis or Steinernema nematodes onto the soil once it reaches at least 60 °F (16 °C), and keeping it moist but not soggy for two weeks. The RHS says to apply in August or early September, before the new grubs grow big enough to do serious damage. It gives 41–68 °F (5–20 °C) for Steinernema products and 54–68 °F (12–20 °C) for Heterorhabditis, and says results are best in open composts and light soils and poor in dry or heavy ones. Steinernema kraussei heads the RHS list of species sold for vine weevil, and the lower Steinernema range means those products can go on in cooler compost. UMass finds nematodes work well against spring grubs in container stock, though results in the landscape have been varied. Koppert lists this weevil among the targets of its Heterorhabditis bacteriophora product. Drenched nematodes are aimed at the grubs; adults are dealt with by hand-picking and traps. Ground and rove beetles, birds, frogs, toads, shrews and hedgehogs all eat adults and grubs.
Cultural controls
Adults cannot fly, so they walk to the plant. That makes night-time hand-picking and barriers worth doing.
- Pick off adults by torchlight on mild evenings, and shake shrubs over a sheet or upturned umbrella
- In greenhouses, look under pots and staging by day, where the adults hide
- Put sticky barriers round pots or staging, or a 6-inch sticky band round the trunks of woody plants
- Repot infested plants and pick out as many grubs from the roots and compost as you can
- Lay burlap or corrugated card at the base of plants as a daytime shelter trap, and check it
- Choose less susceptible cultivars where they exist, and keep a close eye on known favourites
Chemical, last resort
Sources
Penn State Extension, Black Vine Weevil (G.A. Hoover; rev. 2010, updated 2026)
UC IPM Home and Landscape, Black Vine Weevil
UMass Extension Landscape, Black Vine Weevil fact sheet (R. Childs; rev. 2011, updated 2026)
RHS Advice, Vine weevil (RHS Advice Team)
Koppert, Larvanem (Heterorhabditis bacteriophora) product page
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Black vine weevil by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.