How to identify it
- Adults are dark brown to black weevils with small whitish specks and a stout, downward-curving snout, about 9 to 12 mm long.[1]
- Larvae are legless, creamy white grubs with a dark reddish-brown head, about 14 to 17 mm long when full grown.[1]
- Signs on the tree include yellowing then browning needles and blackened pitch around the root collar.[1][2]
Where it lives
Wisconsin and Illinois Extension both cover it on landscape pines.[1][2]
Biology and life cycle
The life cycle takes two to three years; adults emerge from midsummer into early fall, hide by day at the base of the tree or under litter, and feed on shoots on warm nights.[1]
Adults hibernate in litter, bark crevices or soil near the trunk, become active in early May, and females lay eggs in the root collar or soil just beneath the surface.[1]
Larvae hatch in about two weeks and feed on the bark and cambium of the root collar, pupating from late June through mid August.[1][2]
Damage and signs
- It attacks Austrian, Scots and red pine and, more rarely, eastern white pine; young trees 2 to 4 inches across at the soil line can be killed by just two to four larvae.[1]
- Girdling shrinks the trunk below the soil line, so trees may tip over in high winds; adults also wound bark and shoots, causing shoot dieback.[1][2]
Health risk
Control
Prevention
Don't plant pines too deep; the root collar should be just above the soil line. In areas where the weevil is common, avoid large stands of Austrian, Scots or red pine; white pine is less susceptible.[1]
Sanitation
Prune lower branches for light and air, pull competing weeds, and remove needle litter, debris and woodchip or sawdust mulch from around the trunk.[1][2]
Pesticides
Treat the base of the tree in mid May and again in mid August; Wisconsin suggests a soil drench around the root collar with a labeled product containing bifenthrin, permethrin or acephate.[1][2]
Common questions
- Why is my young Scots pine yellowing and leaning?
- Pine root collar weevil grubs girdling the root collar can cause yellowing and tip-over.[1]
- How do I check for pine root collar weevil?
- Pull back the soil and litter at the base and look for blackened pitch and grubs under the bark.[1]
- When should pines be treated?
- Before mid May and again in mid August, after clearing debris from the trunk base.[1][2]
Sources
- University of Wisconsin-Madison Extension (Wisconsin Horticulture), “Pine Root Collar Weevil.” hort.extension.wisc.edu/articles/pine-root-collar-weevil/ (accessed 2026-10-15)
- University of Illinois Extension, “Pales Weevil and Root Collar Weevil.” extension.illinois.edu/insects/pales-weevil-and-root-collar-weevil (accessed 2026-10-15)
- iNaturalist, “Hylobius radicis taxon page (order and family).” www.inaturalist.org/taxa/221939 (accessed 2026-10-06)