On this page
How to identify it
- A tiny reddish-brown beetle only 1.6 to 2.0 mm (about 1/16 inch) long, with a slightly curved snout about a third as long as the rest of its body.[1]
- Newly emerged adults are light brown for about two weeks, with a deep reddish-brown head and snout and black eyes.[1]
- The larva is a white, legless grub with a yellowish head, about 3 mm (1/9 inch) long when grown, found inside a flower bud. The egg is smooth, shiny, pale yellowish and about 0.5 mm long.[1]
- When disturbed, adults drop to the ground and play dead or fly off a few feet.[1]
Where it lives
A native North American beetle. UMass gives its range as Ontario and New England to the Rocky Mountains and Florida; Rutgers researchers list U.S. records from Massachusetts to New Jersey and from Wisconsin and Michigan. It is a major cranberry pest only in Massachusetts.[1][2]
Biology and life cycle
Adults spend late summer, fall and winter under debris and fallen leaves in woods near the crop. In spring they move into blueberry fields (late March through April in New Jersey) and onto cranberry bogs (late May to early June in Massachusetts) to feed on buds and new growth.[1][2]
Females lay eggs once the first flower buds show pink. A female drills a hole into a bud, turns around and lays an egg in it, usually one per blossom, and may lay 50 or more over about three weeks. She often cuts the flower stalk of the bud, which then falls.[1][3]
Eggs hatch in 3 to 9 days, depending on temperature. The grub eats all the flower parts inside the bud and matures in 10 to 14 days, then pupates and becomes an adult.[1]
There is one generation a year. New adults appear while the berries are small and feed on the leaves. Their numbers on cranberry bogs fall sharply toward the end of July, and in blueberries the summer adults move out to nearby woods, where they may feed on other hosts and overwinter.[1][2]
Damage and signs
- The main damage comes from the larvae feeding inside the flower buds. Infested buds change color, from pink to brownish orange in cranberry and to purple in blueberry, fail to open and drop. Uprights with empty flower stalks are often a sign that weevils are present.[1][2]
- Adults drill feeding holes into buds, new growth, leaves and small fruit, leaving black holes on leaves and buds and tiny black spots at the base of dents in small berries.[1]
- Cranberry can make up for some lost flowers: in a Massachusetts study, plants fully compensated when a third of the unopened flowers on a stalk were removed at most sites, but fruit number and weight fell by about 37 percent when two thirds were removed.[3]
- Besides cranberry and blueberry, the weevil uses black huckleberry, staggerbush, dangleberry, sheep laurel, wintergreen, maleberry, sweet pepperbush and other woodland shrubs through the season.[1]
Health risk
It is a bud-feeding weevil of cranberry, blueberry and related shrubs. Neither UMass nor the Rutgers researchers describe any risk to people.[1][2]
Control
Prevention
On cranberry, monitor weekly starting in early to mid May with a sweep net on calm, sunny days, and keep sweep records year after year to follow population trends. In blueberries, adults are sampled with a beat sheet along field edges facing the woods from bud break to early bloom, with a threshold of five adults per bush.[1][2]
Yellow sticky traps hung in the lower half of the blueberry canopy caught the most adults in New Jersey trials, but on their own they have limited use for timing sprays against overwintered weevils.[2]
Biological control
A tiny Habrocytus wasp attacks the weevil inside the blossom buds. In a Massachusetts survey about 40 percent of weevils were parasitized on abandoned bogs, compared with less than 10 percent on commercial bogs.[1]
Pesticides
Sprays target the overwintered adults before they lay eggs in the flower buds. UMass notes that the weevil is hard to manage because it appears resistant to several insecticides, that applications work best in the morning of calm sunny days, and that sanding and flooding are not known to help.[2][1]
Common questions
- Why are my blueberry flower buds turning purple and dropping?
- The cranberry weevil, also called the blueberry blossom weevil, is one cause. Females lay eggs in the flower buds in spring, and infested buds turn purple, fail to open and fall to the ground.[2]
- How big is a cranberry weevil?
- Very small: about 1/16 inch (1.6 to 2.0 mm) long, reddish brown, with a slightly curved snout about a third as long as its body.[1]
- Where do cranberry weevils spend the winter?
- As adults, mostly under debris and fallen leaves in the woods around the bog or field. They return to the crop in spring.[1][2]
Sources
- UMass Amherst Center for Agriculture, Food, and the Environment, “Cranberry Weevil (1999), Cranberry Station fact sheet.” www.umass.edu/agriculture-food-environment/cranberry/fact-sheets/cranberry-weevil-1999 (accessed 2026-11-09)
- Journal of Insect Science (Entomological Society of America); PMC5830975, “Silva, Salamanca, Kyryczenko-Roth, Alborn and Rodriguez-Saona 2018. Comparison of trap types, placement, and colors for monitoring Anthonomus musculus adults in highbush blueberries. Journal of Insect Science 18(2):3.” pmc.ncbi.nlm.nih.gov/articles/PMC5830975/ (accessed 2026-11-09)
- Journal of Economic Entomology (Entomological Society of America); PubMed 14994808, “Long and Averill 2003. Compensatory response of cranberry to simulated damage by cranberry weevil (Anthonomus musculus Say). Journal of Economic Entomology 96(2):407-412 (abstract).” pubmed.ncbi.nlm.nih.gov/14994808/ (accessed 2026-11-09)
- iNaturalist, “Anthonomus musculus taxon page (order and family).” www.inaturalist.org/taxa/63745 (accessed 2026-11-09)