Cranberry Fruitworm

How to identify it

• Look for small, shrunken berries that turned blue early with a pin-sized entry hole near the stem.^[1]
• Later, masses of brown frass and silk web berry clusters together.^[1]
• Adults are small, brown moths that appear around bloom.^[1]

Where it lives

Penn State Extension covers it in blueberry plantings in Pennsylvania.^[1]

US map: public records from 22 states since 1990 (GBIF). View the map

Biology and life cycle

It overwinters as a full-grown larva in litter under the bushes.^[1]

Females lay eggs in the calyx cup as berries begin to form, and larvae enter the berries soon after hatching; there's one generation a year.^[1]

Damage and signs

• Infested berries shrivel and are webbed together with frass and silk.^[1]

Health risk

It feeds on plants; Penn State Extension mentions no risk to people.^[1]

Control

Sanitation

Pick and destroy webbed berry clusters, which also helps against cherry fruitworm.^[1]

Repeated disking to remove weeds and trash also helps control it.^[1]

More on where it's found

It's found across eastern North America from Florida to Nova Scotia and west to Wisconsin and Texas, with small populations reported in the Pacific Northwest.^[2]

Common questions

Why are some of my blueberries shriveled and webbed together?

Cranberry fruitworm larvae web berry clusters together with silk and brown frass.^[1]

How do I control cranberry fruitworm in a home planting?

Pick off and destroy infested, webbed clusters.^[1]

Sources

1. Penn State Extension, “Cranberry Fruitworm on Blueberries.” extension.psu.edu/cranberry-fruitworm-on-blueberries (accessed 2026-10-06)
2. University of Florida IFAS Extension (Featured Creatures), “Cranberry Fruitworm Acrobasis vaccinii Riley (Lepidoptera: Pyralidae).” edis.ifas.ufl.edu/publication/IN1306 (accessed 2026-10-14)
3. iNaturalist, “Acrobasis vaccinii taxon page (order and family).” www.inaturalist.org/taxa/1295940 (accessed 2026-10-06)