Plants > Plant Pests > Apple Maggot  

Rhagoletis pomonella (Walsh) - Apple Maggot

BACKGROUND

The apple maggot is indigenous to North America and has been a serious pest of apples in Canada for over 100 years. The first official record of the pest was at Aldolphustown, Ontario in 1896. By 1905 the insect had extended its area to Como and St. Hilaire, Quebec. A few years later it was found near Digby, Nova Scotia. It is now widespread throughout eastern Canada, with the exception of Newfoundland.

HOSTS

The principal hosts of the Apple Maggot are apple (Malus spp) and hawthorn (Crataegus spp); sweet cherry (Prunus avium) and sour cherry (Prunus cerasus) are also significant hosts in two states of the U.S.A. Other hosts are known.

DISTRIBUTION

• North America:
  • Canada: (PEI, NB, NS, PQ, ON, MB, SK)
  • USA: (AR, CA, CO, CT, DE, FL, GA, ID, IL, IN, IA, KS, ME, MD, MA, MI, MN, MS, NE, NH, NJ, NY, NC, ND, OH, OR, PA, RI, SC, SD, TX, UT, VT, VA, WA, WV, WI)
  • Mexico: Northern and Central; Hidalgo (Zaqualtipan, central highlands); Nuevo Leon (Mt El Potosi); Veracruz (Jalapa and Perote areas).

BIOLOGY

The apple maggot has only one generation a year. Females lay their eggs singly beneath the skin of the fruit. The larvae hatch 3 to 7 days later and tunnel into the fruit pulp. They complete their development within the fruit, taking anywhere from two weeks to several months to mature. Very rarely will larvae exit from hanging fruit. The infested fruit usually drops to the ground. Larvae remain in the dropped fruit until reaching maturity when they make an exit hole in the skin of the fruit and wriggle to the ground. Larval emergence from fruit may continue into early December. Larvae then enter the soil where pupation occurs. They enter the soil to a depth of 2-5 cm, usually beneath the host plant. Pupae stay dormant over winter, and they may persist in the soil for several years. Adults emerge in late June or July and may feed on insect honeydew and bird dung, reaching sexual maturity 7-10 days after emergence. As the flies mature and mate they respond more to oviposition-site stimuli, i.e., fruit shape and fruit odour . After mating, a single female fly is capable of laying more than 200 eggs in her lifetime. The average emergence date for all locations (east and west) is June 23. Adults usually die after 3-4 weeks but may live up to 40 days under field conditions.

DETECTION & IDENTIFICATION

Symptoms:

The apple maggot burrows in all directions through the flesh of apples feeding on the pulp and leaving brown channels. When a single fruit is infested with several larvae the pulp will be honeycombed with their burrows until it finally breaks down. Infested fruit are usually misshapen (Fig.1). Oviposition punctures are surrounded by tissue discolouration and usually appear as a black spot.

Identification:

The adult is about 2-4mm long, a little smaller than the housefly, easily recognizable by four irregular or zig-zag black bands on the wings (Fig. 2). The body is generally black with a yellowish head and legs and greenish eyes. The male has three white bands on the abdomen and the female has four similar white bands and is considerably larger. The eggs are elliptical, semi-opaque and creamy white, with both ends slightly yellow and more opaque, about 0.9 mm long and 0.23 mm wide. The legless larva when fully grown are usually 6.5 - 8 mm in length and 1.5 - 2 mm in width at the widest point. The cream-coloured body consists of 11 apparent segments (Fig. 4). The oval-shaped, yellow-brown in colour pupae are approximately 5 mm in length and 2.3 mm wide (Fig. 5).

Fig. 1 (96K)

Fig. 2 (61K)

Fig. 3 (44K)

Fig. 4 (118K)

Fig. 5 (61K)

Text: S. Wallace, Plant Health Risk Assessment Unit.
Photo : Agriculture & Agri-Food Canada, Research Branch, Ottawa