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How to identify it
- Adults are 2 mm long, teardrop-shaped, with lengthwise ridges on the wing covers. They are black when they first emerge from pupation, but after a few days of feeding they become coated in rust-colored deposits derived from the plant sap, so most adults seen on the vine look rusty orange-brown.[1]
- Their feeding punches a characteristic shot-hole pattern into the young triangular leaves of mile-a-minute, and adults are easy to spot feeding and laying eggs on the stems and leaves throughout the growing season. If you cannot find adults, the shot holes confirm they are there.[1]
- Eggs are tan, cylindrical and dotted with small deposits of darker frass, laid singly on buds, stems and leaves. Larvae are creamy yellow with a brown head, up to 3 mm, and live inside the stem; split a deformed or damaged stem to find them.[1]
Where it lives
Native to Asia. Populations sourced from China were released in the northeastern and Mid-Atlantic United States beginning in 2004, and the weevil is now widely distributed throughout both regions, with populations that are typically high and have dispersed rapidly from most release sites.[1]
Biology and life cycle
Adults emerge in early spring and feed on the young leaves. A female lays 40 to 130 eggs, singly, on buds, stems and leaves; the hatching larva burrows into a node and feeds inside the stem through three stages, then drops or crawls to the soil to pupate. Egg to adult takes three to four weeks, there are three to four generations a year, and adults of the last generation overwinter in the soil or plant litter.[1][2]
The weevil prefers sunny places. It survives in both dry and moist conditions, but its impact on the weed is highest at warm, dry sites.[1]
It hunts along edges. University of Delaware researchers released weevils at a forest edge and found more than twice as many on potted vines 2 metres away as at 6 or 14 metres; at 14 metres, six to eight times as many weevils reached vines along the forest edge as vines in the open field or inside the woods. Weevils released in the open flew off in all directions but still ended up mostly on edge plants. The weevil seems adapted to find its host where the vine grows, in riparian corridors in Asia and along forest edges here, so it moves well between patches along wooded edges but may not find isolated patches in the open or deep in the forest.[3]
The weevil has been mass reared for release for 8 to 9 years, 24 to 36 generations, without any new wild stock. Compared with field weevils, the colony insects laid more eggs, survived less well and responded less to the cues that trigger reproductive diapause; for both, exposure to older plants mattered more than day length or temperature in inducing diapause, and at least part of the lab population overwintered successfully, so the researchers saw no need yet to add wild genes.[4]
Damage and signs
- Larval mining weakens the stems and stunts growth, adult feeding at the stem tips cuts growth and seed production, and heavy defoliation makes leaves and stems curl and wither. At high weevil densities the combined feeding kills the vines.[1]
- Results vary. The weevil has been documented reducing mile-a-minute density, cover and seed production, but the effect changes from year to year and some weed populations escape in some years. The biggest reductions in density and biomass come where other vegetation competes with the vine, and in warm, dry years; cool, moist conditions, especially in spring, blunt the impact. Penn State sums it up: weevil infestation does not eradicate mile-a-minute, but it does severely stunt the plant's growth. No nontarget effects have been reported.[1][2]
Health risk
A weevil that feeds solely on mile-a-minute; none of these sources describes any risk to people.[2][1]
Control
Prevention
Give the weevil help: it does most where competing vegetation is present and the site is sunny, warm and dry, and it finds new patches along wooded edges far more readily than isolated patches out in the open or inside a forest, so isolated patches may be slow to pick up weevils on their own.[1][3]
Traps and physical control
Small infestations of the vine can simply be pulled, with long sleeves and leather gloves against the barbs; before June, when the seed begins to mature, pulled plants can be left on site to dry.[2]
Biological control
The weevil is the control. Sale of the weevil is regulated by USDA APHIS, but Penn State notes it is legal to move weevil-infested plant material to new sites within the same state.[2]
Common questions
- Why are the weevils on my vines orange instead of black?
- Freshly emerged adults are black. Within a few days of feeding they become coated in rust-colored deposits from the plant sap, so the orange-brown weevils are simply older ones.[1]
- Can I collect weevils and move them to another patch?
- Within the same state, yes; Penn State notes that distributing infested plant material to new sites in the same state is legal, while selling the weevil is regulated by USDA APHIS. The weevil lays eggs on buds, stems and leaves, so infested vine carries the next generation.[2][1]
- The weevils were abundant last year but the vine came back. Why?
- Impact swings with the weather and the site. It is greatest in warm, dry years and where other plants compete with the vine, and lowest after a cool, moist spring, so some weed populations escape in some years even where weevils are numerous.[1]
Sources
- North American Invasive Species Management Association (PDF hosted on Bugwood), “Hough-Goldstein (University of Delaware) and Lake (Mt. Cuba Center). Mile-a-minute Weed Biocontrol Agents: History and Ecology in North America. In: Winston, ed., Biological Control of Weeds in North America, NAISMA-BCW-2022-11-MILE A MINUTE WEED-A (2022).” bugwoodcloud.org/resource/files/26410.pdf (accessed 2026-11-10)
- Penn State Extension, “Mile-a-Minute.” extension.psu.edu/mile-a-minute (accessed 2026-11-10)
- Environmental Entomology (Entomological Society of America), “Hough-Goldstein, Lake, D'Amico and Berg (University of Delaware). Preferential edge habitat colonization by a specialist weevil, Rhinoncomimus latipes (Coleoptera: Curculionidae). Environmental Entomology 41: 1466-1473 (2012), doi:10.1603/EN12090.” doi.org/10.1603/EN12090 (accessed 2026-11-10)
- Environmental Entomology (Entomological Society of America), “Hough-Goldstein, Stout and Schoenstein (University of Delaware). Fitness and field performance of a mass-reared biological control agent, Rhinoncomimus latipes (Coleoptera: Curculionidae). Environmental Entomology 43: 923-931 (2014), doi:10.1603/EN14019.” doi.org/10.1603/EN14019 (accessed 2026-11-10)
- iNaturalist, “Rhinoncomimus latipes taxon page (order and family).” www.inaturalist.org/taxa/366560 (accessed 2026-11-10)