Pest profile

Blueberry Maggot

Rhagoletis mendax · Diptera: Tephritidae[3]

The blueberry maggot is a small fruit fly with banded wings whose maggots feed inside ripening blueberries, one per berry, often going unnoticed until they crawl out after harvest.[1][2]

Blueberry maggot fly with dark-banded wings resting on a berry
Blueberry maggot fly with dark-banded wings resting on a berry. Blueberry maggot by Jerry A. Payne, USDA Agricultural Research Service — via Wikimedia Commons, CC BY 3.0

How to identify it

  • Adults are about 3/16 inch long and look like small house flies with dark bands on the wings.[1]
  • Larvae are legless maggots up to 5/16 inch long, with a single hook-like tooth at the mouth end.[1]
  • Infested berries turn soft as the maggot develops.[1]

Look-alikes

Look-alikeHow to tell them apart
Apple maggotAdults are virtually identical in size and wing pattern, but apple maggot does not feed on blueberries.[1]

Where it lives

It has damaged blueberries in the eastern and southern US and eastern Canada; Wisconsin first detected it in 2016, and UNH covers it in New England wild (lowbush) blueberries.[1][2]

Biology and life cycle

Adults fly from June or July through August; females feed for about a week, then lay single eggs under the skin of nearly ripe berries, up to 100 each.[1]

Eggs hatch within a week; each maggot feeds two to three weeks in one berry, then drops to overwinter as a pupa in the top few inches of soil, and some pupae wait two or three years to emerge.[1]

In wild blueberry fields, the flies are weak fliers that come in low from forest edges.[2]

Damage and signs

  • Highbush blueberry is the only commercially grown fruit it attacks; wild hosts include wild blueberries, lingonberry, deerberry and huckleberry.[1]
  • Damage usually first appears in mid July and continues until harvest; maggots may show up in fresh fruit or jams and pies.[1]

Health risk

None to people or pets.[1][2]

Control

Prevention

Starting a few weeks before berries ripen (usually early June), hang yellow sticky cards baited with ammonium acetate or carbonate, folded in a V with the yellow facing down.[1][2]

To check fruit, crush 100 berries in salt water (1 part salt to 4 parts water); floating larvae give the percentage infested.[1]

Sanitation

Harvest thoroughly, and heat to at least 120°F or freeze damaged fruit before composting; remove weeds and nearby wild blueberry and huckleberry plants, and clean soil off equipment moved between patches.[1]

Pesticides

Wisconsin starts sprays when traps average more than one fly for several days in a row, repeating every 7 to 10 days through harvest; UNH notes border treatments in wild blueberry fields.[1][2]

Common questions

Why are there little white worms in my blueberries?
Likely blueberry maggots, which feed inside ripening berries.[1]
How can I tell if my blueberries are infested?
Crush a sample of berries in salt water; larvae float to the surface.[1]
Can I compost infested blueberries?
Heat or freeze them first; pupae survive in compost and can reinfest the patch.[1]

Sources

  1. University of Wisconsin-Madison Extension (Wisconsin Horticulture), “Blueberry Maggot.” hort.extension.wisc.edu/articles/blueberry-maggot/ (accessed 2026-10-15)
  2. University of New Hampshire Extension, “Over-informed on IPM, Episode 015: SWD and Blueberry Maggot (August 2019).” extension.unh.edu/blog/2019/08/over-informed-ipm-episode-015-swd-blueberry-maggot (accessed 2026-10-15)
  3. iNaturalist, “Rhagoletis mendax taxon page (order and family).” www.inaturalist.org/taxa/52205 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.