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Cherry fruit fly

 

               There are two species of cherry fruit fly in Minnesota that lay eggs in ripening cherry fruit: the eastern cherry fruit fly and the black cherry fruit fly. Both cherry fruit flies are native to the Upper Midwest and only infest cherry species, including sour cherry, sweet cherry, black cherries and pin cherries. The eastern cherry fruit fly is the more common species in Minnesota cherry trees.

 

Identification

 

               Cherry fruit flies are about 1/4 inch long, or about the size of a house fly. Both the eastern cherry fruit fly and the black cherry fruit fly have a black thorax, and a black abdomen with white stripes. The two cherry fruit flies have distinct bands on clear wings that can easily be seen with the naked eye. The bands of the black cherry fruit fly are black, while those of the eastern cherry fruit fly are grayish, and the bands on each species have distinctly different patterns. Cherry fruit fly adults are nearly twice as large as SWD adults.

 

               Cherry fruit flies have cream-colored maggots. They have a maximum size of 1/4 inch with a cylindrical shape that tapers towards the head. There is typically only one maggot per cherry. The larvae of these fruit flies are very difficult to distinguish between those of spotted wing Drosophila (SWD). It is best to determine what insect is present by monitoring for the adults.

 

 

Damage

 

               Cherry fruit flies turn the cherry fruit flesh brown and will often eat the majority of the flesh inside a cherry, making the fruit unacceptable for either eating fresh or for pies. Cherries infested with maggots often decay or develop brown rot. Cherry fruit flies are locally abundant in southern Minnesota, where some trees will have a maggot in nearly every cherry.

 

Important biology

 

               Cherry fruit flies have one generation per year. Adults emerge from the soil in late June and early July and females seek out suitable hosts to deposit eggs. Cherry fruit flies have a narrow host range, laying their eggs in cherries, including tart cherries and wild pin cherries. The flies emerge one to two weeks before they start depositing eggs. Egg laying usually begins when the cherries are turning yellow and continues for another month. The female pierces the fruit with her ovipositor and inserts a single egg just below the surface. The larva hatches 4 to 7 days later, and the maggot burrows through the cherry flesh towards the pit. The larvae remain near the pit as it matures, but will often bore a hole at the bottom of the cherry to get access to air. After about two to three weeks, the larva bores through the skin and drops to the soil where it pupates. The pupa stays in the soil until the following summer.

 

 

 

Management

 

Monitoring

 

               Monitor cherry fruit flies to determine when the flies are active and estimate pest pressure. The most common method to monitor for cherry fruit flies is with yellow sticky cards. Place the cards in the tree canopy shortly after bloom.

 

Sanitation

 

               Remove and dispose of all infested fruit to help prevent the cherry fruit flies from overwintering next to producing trees. The population of cherry fruit flies will grow from year to year if larvae are allowed to pupate and overwinter in the soil below the cherry trees when infested fruit is not removed.

 

Insecticides

 

               When using an insecticide, apply it before adult flies start depositing their eggs in the ripening cherries. Adult cherry fruit flies emerge one to two weeks before they start depositing eggs. The first insecticide should be applied as soon as the first adults are caught on sticky cards. If necessary, a second spray can be applied ten days later. Insecticides that can be used to control cherry fruit fly are acetamiprid, carbaryl, malathion and spinosad.