Fruit IPM Fact Sheet

Species—Rhagoletis mendax Curran

Description

The adult is a black fly with 3 or 4 white bands across the abdomen and a W-shaped pattern of dark bands on its wings. It is 1/5 inch long, a bit smaller than a house fly. The immature forms are maggots that are white, legless and about ¼ inch long when fully grown.

Life History:

This pest overwinters in the pupa stage in the soil. Adults emerge over a prolonged period from late June to early August. The female flies do not begin laying eggs until about 10 days after emergence. Flies alight on fruit to lay one egg per berry under the fruit skin just as the fruit begins to turn blue. The egg hatches in about one week. Maggots feed for about three weeks inside ripening and harvested fruits. There is one generation per year.

Egg: The egg is whitish, oval and 1 mm long.

Larva: Larvae hatch from the egg 2 to 7 days after oviposition. The maggot tunnels throughout the fruit, liquefying the flesh as it matures. Small larvae are colorless, making their detection almost impossible, but older larvae can be found inside berries due to their size, the whitish clouding of their bodies, and the destruction of the fruit flesh. Infested fruits are soft and may bear a depression or hole at the point of egg insertion. Full-grown larvae or maggots measure 7 mm long. Larvae are glossy white or yellowish and legless, and they taper toward the head end. Maggots lack obvious segments. Segmented worms are either cranberry fruitworm or cherry fruitworm. Under magnification, two mouth hooks may be seen at the head end. After about twenty days inside the fruit, the larvae drop to the ground to pupate.

The blueberry maggot overwinters as a puparium, buried in the soil below the bushes. The puparium looks like a seed: it is brown or yellowish brown, somewhat barrel-shaped, and about 1/8 inch long. Emergence from the puparium is affected by many factors, soil moisture and temperature, depth of the puparium, and chilling during the winter months. In regions with relatively mild winters, a puparium may lie dormant more than one year if a sufficient cooling period is not obtained in the first winter. Emergence usually begins in mid-June and continues through much of the summer.

The adult fly is slightly smaller than a housefly, with a black and dark-gray body and one pair of wings marked with distinctive black bands; the adult has a distinct white to cream-colored marking on its thorax and thin banding of the same color on the abdomen. Adult females lay eggs about 7 to 10 days after they emerge. Eggs are usually inserted just under the skin of ripening or ripe berries, although some may oviposit in green fruit. Generally, only one egg will be laid per berry, apparently due to a marking pheromone produced by ovipositing females.

Damage and Importance

The blueberry maggot is generally the most serious pest of blueberry production in the eastern United States. Berries become soft, mushy and unmarketable from maggots feeding within the berries. If undetected, infested berries will contaminate the packout. Without pesticide treatments in some fields, nearly all of the berries may be infested, even in some otherwise well managed fields. This is especially true if commercial fields are near abandoned or wild blueberries. There is zero tolerance for blueberry maggots in berries sold for processing; one maggot detected by inspectors can result in the refusal of an entire shipment. When preserves are made from infested berries, the maggots rise to the top after processing and can be found just under the lid of the container.

Determining the onset of adult fly activity is essential to the control of blueberry maggot, as protective sprays must be applied before the 7- to 10- day pre-oviposition period ends. Adult files can be trapped on yellow sticky boards; the catch will be enhanced if the boards are baited with protein hydrolysate and ammonium acetate. Commercially available yellow sticky board traps for apple maggot adults can be used effectively. Traps most commonly used are yellow cardboard or plastic. These can be bent in half, sticky side down, to form a V pointing downward; traps can be suspended from angled stakes so that the bottom of the trap is 6 to 10 inches above the canopy. Place traps along field borders. Use at least three traps per field or one trap per acre. Set traps up in early June. Check traps twice per week, replacing sticky panels every 2 to 3 weeks. Traps should be placed on the perimeter of commercial fields, or just outside of commercial fields in abandoned or wild blueberries if these are nearby. Blueberry maggot adults generally do not enter managed fields until some time after emerging in wild areas; adults may have already passed through their pre-oviposition period by the time they appear in commercial fields. Traps in nearby wild areas will provide a more timely indication of maggot activity. Sustained catch of the blueberry maggot fly in traps indicates that it is an optimal time to make an insecticide treatment; sustained catch means not just the first one or two flies, but consistent catch of several flies per week. Once adult activity has been detected and the timing of the first protective spray determined, monitoring may be discontinued. Pesticide treatments must be continued on a regular schedule through the end of harvest in order to adequately protect the fruit from infestation by the blueberry maggot where this pest is a problem. Clean harvest and prompt picking may provide a small amount of control.
See the Fruit CAT Alert Article, Monitoring for Blueberry Maggot flies by Rufus Isaacs

At least two species of parasitic wasp in the family Braconidae attack the blueberry maggot in the eastern United States, sometimes causing up to 40% mortality. These wasps may soon become available commercially for use in biological control. Ants also provide natural control by their predation on larvae and pupae in the soil. Unfortunately, parasitism and predation do not have a great effect on maggot infestation, so pesticides are often needed to produce clean fruit.

Mechanical Control: In small plantings, it may be possible to trap-out this insect if trap density is sufficient; one sticky trap per bush is suggested.

Control by Insecticide: Insecticide is effective if directed at adult flies before they lay eggs. This is usually close to harvest, so care must be taken to obey the required preharvest interval specified on each insecticide label. For currently recommended pesticide controls see E-154, The Michigan Fruit Management Guide. Rufus Isaacs has an article on blueberry insecticides in the June 28, 2005 Fruit CAT Alert.

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Created: July 11, 1998
Modified: February 26, 2005