Scientific Name—Rhagoletis cingulata (Loew)

Reference: Common Tree Fruit Pests Angus Howitt, 1993, NCR 63 Michigan State University

Three species of pictures-winged fruit files attack stone fruits in the north central states. Two species, the cherry fruit fly and the black cherry fruit fly, attack sweet and tart cherries and wild species of cherries. The apple maggot fruit fly is primarily a pest of apples but will attack plums and prunes late in the season.

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

Larva: Full-grown larvae or maggots measure 7 mm long. Larvae are glossy white or yellowish and legless, and they taper toward the head end. Under magnification, two mouth hooks may be seen at the head end.

Pupa: The puparium is golden brown to dark brown, resembling a grain of wheat, and is approximately 4 mm long.

Adult: The adult flies are blackish with yellowish head and legs. They measure about 4.5 mm long, about two-thirds the size of the housefly. Near the center of the back is a small cream or yellow dot. The two species of flies are distinguished by prominent dusky bands or markings on the wings and by markings on the body. The body of the black cherry fruit fly is entirely black, while the abdomen of the cherry fruit fly is black with white transverse bands across it, four bands on the female and three on the male. The cherry fruit fly is usually by far the more abundant species.

In addition to cultivated sweet and tart cherries, one or both species have been found in wild black cherry, pin cherry, mahaleb cherry and choke cherry. Cherry fruit flies have been reported from all sections of the north central states where cherries are grown. Normally, pin cherry is the wild host for the black cherry fruit fly, and wild black cherry is the host for the cherry fruit fly.

Damage to the fruit occurs in two ways: feeding by the adults and feeding by the maggots. Oviposition injury by the adult may occur from egg laying. Punctures made by the female’s ovipositor are usually made near the bottom of the fruit. Up to 40 eggs have been reported as being deposited in a single fruit. Normally, only one maggot develops in each fruit, even though many eggs may have been deposited in that fruit. Primary damage results from the feeding of the larva within the fruit. Infested fruits appear normal until the maggot is nearly full-grown, at which time sunken spots appear. Maggots and their frass within the fruit render the product unsalable. Infested fruit is more susceptible to brown rot and other diseases, so materials used to inoculate for disease in the orchard should be increased.

The time of adult emergence varies with the season and appears to be early or late in direct relation to the temperature and rainfall, especially during late May and early June. Seasons with an even distribution of rainfall and moderate temperatures appear very favorable for the development of the species. Normally, a rainfall sufficient to wet the upper inch of soil is required before flies will emerge from the soil. Conversely, extended drought periods are unfavorable for emergence, and during such periods, fly emergence is likely to be irregular. Extremely hard-baked soil at the time the maggots are entering the soil will reduce the population significantly.

Mechanical harvesting of cherries leaves some cherries on most trees for some weeks; any pesticide that was present on the fruit at harvest degrades or is washed off the remaining fruit. Fruit flies from wild hosts, particularly wild black cherry, emerge for some time after cherry harvest. These flies are able to infest cherries left on the trees. The larvae complete their development, pupate in the soil and infest the orchard the following year.

For all practical purposes, the two species of fruit flies can be considered as one because the life cycles and control measures for them are almost identical.

The cherry fruit fly spends about 10 months of the year in the soil beneath the trees in a puparium resembling a grain of wheat. In late May, the pupae transforms to the adult flies and, depending on location start emerging from the ground. Peak emergence for the black cherry fruit fly is about mid-June; that of the cherry fruit fly is about harvest time (mid-to-late July). Normally, the black cherry fruit fly will emerge 10 days to two weeks earlier than the cherry fruit fly. The adult flies spend about 10 days feeding in the tree (this is the preoviposition feeding period) before they lay eggs. The adult flies are active on warm, bright days, feeding on the surface of the leaves or fruit on drops of dew, plant juices or honeydew secretions from aphids, or from feeding punctures in the fruit. The feeding habits of these insects, and the fact that there is a preoviposition feeding and mating period, present a means of control; i.e., the application of insecticides to kill the adult flies before they can lay eggs.

The female inserts eggs beneath the skin of the fruit through a needle-shaped ovipositor. Eggs are most frequently inserted on the sides of the fruit. Each female is capable of laying 300 to 400 eggs during the three to four weeks she is active. The eggs hatch in five to seven days, and the legless maggots start to feed around the pit and later in the pulp of the cherry. Maggots feed for approximately two weeks. When full grown, they drop to the ground and burrow into the soil. They usually burrow 1 to 2 inches beneath depths up to 5 inches.

The maggot constructs a puparium in the soil and overwinters. Only one generation of cherry fruit flies occurs each year, though some of the puparia may remain in the soil for two years.

In June, hang canary-yellow, sticky traps in the foliage of cherry trees. Cherry fruit flies respond to high concentrations of ammonia, so add a teaspoonful of ammonium acetate or ammonium hydroxide to the trap before hanging. Identify each species and its abundance by examining the banding on the wings. The black cherry fruit fly will emerge 10 to 14 days earlier than the cherry fruit fly. Treat within five to six days after the first catch.

The flies must be controlled with effective chemicals in the eight-day preoviposition period before the female matures and she can lay eggs. Bait traps that are colored canary-yellow, coated with a sticky material, and baited with a feeding attractant such as ammonium acetate or protein hydrolysate should be employed for monitoring the emergence of the fruit flies.