Rhagoletis mendax (Blueberry Maggot) - Fact Sheet

Background

The blueberry maggot was first detected in Maine and New Hampshire in 1914. Since its first detection it has become a important pest of commercially grown low bush and high bush blueberries in the Canadian Maritime Provinces. Although common to most of the blueberry areas in the Maritimes it does not occur in Newfoundland. The concern over this insect is not due to the crop losses caused by larval feeding, but to the unmarketability of the maggot infested fruit.

Hosts

The primary host of the blueberry maggot is blueberry, both high bush (Vaccinium corymbosum) and low bush (V. angustifolium, V. myrtilloides and V. vacillans). Other suitable hosts include Hillside blueberry (V. pallidum), Deerberry (V. stamineum) and Huckleberry (Gaylussacia spp). Additional hosts have been reported in the literature, but these hosts need to be substantiated mainly, Black chokeberry (Aronia melanocarpa), Bunchberry (Cornus canadensis), Mountain juneberry (Amelanchier bartramiana), Wintergreen (Gaultheria procumbens) and Mountain cranberry (V. vitis-idea).

Distribution

North America:

  • Canada (Prince Edward Island, Nova Scotia, New Brunswick, small isolated populations have been detected in southwest Ontario and southwest Quebec)
  • United States of America (Alabama, Connecticut, Delaware, District of Colombia, Florida, Georgie, Indiana, Illinois, Kentucky, Maine, Maryland, Massachusetts, Michigan, Missouri, New Hampshire, New Jersey, New York, North Caroline, Ohio, Pennsylvania, Rhode Island, South Caroline, Tennessee, Virginia, West Virginia, Wisconsin).

Biology

The blueberry maggot spends the winter in the pupal stage in the upper few inches of the soil.The first adults emerge from late June to mid-July depending on weather and locality. After emergence, the adults continue their sexual maturation by feeding on nectar, honeydew and bird droppings they find on vegetation. The adults cause no visible damage to the plants and are unlikely to be seen. Blueberry maggot flies tend to form stable, local populations that infest the same locality year after year. They seldom make long distance flights preferring instead to move from leaf to leaf or from one plant to another. One to two weeks after emergence the adult females begin to mate and to lay eggs, one in each berry. Each female lays from 25 to 100 eggs over a 2 to 3 week period. Egg laying may continue until early September with the majority of eggs being laid during the latter part of July and early August. The developing maggots consume the pulp of the berry causing it to collapse. At the end of the larval stage, the larvae exit the fruit and drop to the soil. The larvae burrow into the soil to a depth of 5 cm and pupate. Most of the pupae emerge as adults the following year. Between 5 and 20% of the pupae may remain in the soil and emerge in the second year. Approximately 1% of the pupae may remain in the soil and emerge in the third or fourth years.

Life Cycle of R. mendax

Blueberry Maggot Life Cycle. Description follows.
Cycle of Rhagoletis mendax

This image illustrates the life cycle of Rhagoletis mendax and shows:

  • that the pupal stage (in the soil) ends as late as mid-August
  • the Rhagoletis mendax can remain in the pupal state for six months to four years
  • the relative size and markings of the male and female adults
  • the relative size of the egg and larvae

The image also shows how to identify the adult Rhagoletis mendax compared to Rhagoletis pomonella.

Illustration courtesy of Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec

Detection & Identification

Symptoms: Infested fields will have an abundance of fruit on the ground. Puncture holes will be visible on the skin of berries (Figure 3). Collapsed berries will also be common (Figure 5).

Identification: The adult fly is approximately 4.5 millimetres in length with a wingspan of about 8 millimetres. The wings display a brown banding pattern while the black abdomen is marked with white cross bands (Figures 1 and 2). It should be noted that, accurate identification requires specialized expertise. To the naked eye, the Blueberry maggot is virtually identical to the Apple maggot, Rhagoletis pomonella (Walsh). The legless, whitish-coloured larvae are up to 8 millimetres in length (Figure 4). The oval-shaped pupae are approximately 6 millimetres in length and are yellow-brown in colour (Figure 6).

Adult fly
Figure 1
Adult fly
Figure 2
Puncture holes visible on the skin of berries
Figure 3
Larvae
Figure 4
Collapsed berry
Figure 5
Oval-shaped pupae
Figure 6

Photos: Agriculture & Agri-Food Canada, Research Branch, Ottawa
Life Cycle Diagram: Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec

Date modified: