Notes on Blueberry Insects: Blueberry maggot

Blueberry maggot is a regulated pest. The federal Plant Protection Act and Regulations place movement restrictions on blueberry fruit, plants, soil and containers from areas known to be infested with blueberry maggot. These laws exist to prevent the spread of this pest from infested areas, such as Nova Scotia, New Brunswick, Prince Edward Island, Maine, New York, Michigan, to non-infested areas, such as Ontario, Quebec and B.C. All infestations of blueberry maggot must be reported to the Canadian Food Inspection Agency.


The adult blueberry maggot is a fly that is slightly smaller than a housefly. It has a grey-black body with a white spot and distinct dark banding on its wings (see Figure 1). Wing patterns of apple maggot and other related species. The immature stage is a white larva that infests blueberry fruit (See Table 1).

Insect pest Head Legs
Plum curculio Brown head capsule No legs
Cranberry fruitworm Brown head capsule Has 3 pairs legs plus prolegs
Blueberry maggot No head capsule No legs

Period of activity

In early July, as the first berries are turning blue, adult flies begin to emerge from pupae in the soil. Emergence and adult activity continues into August. Adult flies lay eggs on developing blueberry fruit and larvae develop inside the fruit. Infested fruit may ripen and soften prematurely. Mature larvae emerge from dropped fruit, then pupate and overwinter in the soil beneath the bushes.

Monitoring and thresholds

Monitor for blueberry maggot flies using yellow sticky traps baited with ammonium acetate. These traps are also used for apple maggot. Place traps in the top 1/3 of the bush, by mid-June, on the perimeter of commercial fields. If abandoned or wild blueberries are nearby, place traps just outside of commercial fields. Clear plant foliage away from the trap so it is plainly visible. See Pest Monitoring Equipment Suppliers on the OMAFRA website.

Management notes

Insecticides and timings for blueberry maggot control are listed in the OMAFRA Publication 360 Blueberry Calendar.

  • The township of Wainfleet in Niagara region, the township of Charlotteville in Norfolk and specific sites in Brant and Elgin counties have restricted areas with quarantines in place to eradicate blueberry maggot and to prevent its spread.
  • In restricted areas, begin sprays for blueberry maggot when berries begin to turn blue or when the first maggot flies are detected on traps. In other areas, spray the border of the planting (outer six to eight rows of blueberries) to reduce the risk of infestation.
  • Monitor new plantings closely for blueberry maggot, especially if planting stock originated in an infested area.
  • Do not use Cygon or Lagon on blueberries destined for markets in the United States because there is zero tolerance for the active ingredient dimethoate on blueberry fruit in the USA.
  • If blueberries are bought for re-sale on your farm, do not throw away the culls and unmarketable berries. Deep burial, below the plough layer, is the best way to dispose of this material.

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Author: OMAFRA Staff
Creation Date: 17 May 2006
Last Reviewed: 17 May 2006