Species

Cherry Fruit Fly (Rhagoletis cingulata)
Class: Insecta
Order: Diptera

Related species
The cherry fruit fly (CFF) is related to the western cherry fruit fly, Rhagoletis indifferens, which inhabits the Pacific Northwest, and the black cherry fruit fly, Rhagoletis fausta, found further east in the US.
CFFs are also similar to apple maggots and blueberry maggots. Color and wing features can differentiate these insects.

Host/Site

CFFs are found in sweet or tart fruit producing cherry trees and some wild cherry tree species. They are also sometimes found in plum trees. They are the primary pest in non-commercial, or home cherry orchards.

CFFs are monitored carefully commercially, since larvae found in a cherry can prove detrimental to a farmer's harvest. Farmers must ensure there are no larvae in cherries ready for packaging and shipment. Farmers use insecticides consistently to remove all infestations during the growing season.

Identification

Appearance
Adults are black flies with yellow and white markings across the abdomen. Their heads are yellow and wings have black markings, which are most helpful to differentiate CFFs from other fruit flies. Larva is white and similar to a maggot, usually 5-6 mm long. Pupa can be slightly browned, 4-5 mm in length.

Indicators
Fruit will not look abnormal until larvae are fully grown. If larvae are developed, the cherry can have cavities, depressions (bruises), and shriveled areas along the surface.

Small punctures, 1-3 often, indicate a female has deposited eggs into the cherry.

If infested fruit is discovered, oftentimes most of the tree will be infested as well.

Life cycle
CFFs have a single generation per season. During the summer, they feed on a tree for five to ten days before laying eggs within an unripe cherry. If there is no fruit, CFF's will search for another host. Otherwise, they will confine themselves to one tree.

The egg develops into larvae within the core of the cherry, then burrows out and drops to the soil. This entire cycle can take 20-30 days, taking longer in cool weather.

Most emerge from the fruit one to three weeks after the fruit has turned red.

Once in the soil, they burrow 1-6 inches below the surface and pupate throughout the winter then resurface during the next growing season. Their emergence from the pupal stage can be spread over eight weeks.

Natural Enemies

There are no natural enemies that can adequately reduce and remove a CFF population.

Monitoring

The most common way to detect CFFs early is by using traps. Traps are yellow sticky cards that when baited with ammonium carbonate can attract adult flies.

A trap should be hung within the tree at eye-level in late May or early June. Pay attention to the trap at least twice a week to detect when adults are reemerging from the soil. Remember to look at the black patterns on the wing to determine the species.

Action Threshold

In many regions where non-commercial cherry trees are relatively close to famer's cherry trees, it is illegal not to eliminate infestations. If an emergence of CFFs is noticed controls must be implemented immediately, whether they are physical, biological, or chemical.

Cultural and Physical Controls

If the infestation is isolated to one tree, there are ways to remove the infestations without the use of insecticides.

If the range of the infestation is maintainable, that is, limited to accessible trees, remove all fruit from the tree prior to harvest. This disrupts the larvae from developing within the cherry and falling into the soil for winter; thus, greatly reducing next year's population.

Cherries left on the infested tree or on the surrounding ground can often increase the population of CFFs for next year's harvest. Be sure to not leave any traces of cherries in order to reduce the CFF population.
In the following growing season, remove all fruit from the tree again. This will kill any flies/larvae that made it through the winter.

Once the infested tree has all of its fruit removed for two consecutive harvest seasons, the tree should no longer be infested.

Biological Controls

Commercial cherry farmers do not use biological controls since they are required to have 100 percent larvae-free fruit for packaging and sales.

For the home orchard, beneficial nematodes can be helpful, though they will not get rid of the problem entirely. Nematodes can work the soil and eat larvae so as to reduce the population for the following harvest.

If a tree was physically maintained and all fruit was removed during the first season, use nematodes during the following winter to try to reduce the population for the second harvest season. Remember that it is necessary to remove all fruit from the tree during this second season to ensure ridding the tree of a CFF infestation.

Chemical Controls

There are no toxic-free alternatives that have been accepted by the cherry farming community as yet. There are, however, certain treatments that are allowed for organic cherry farming, which are lower in toxics.

Entrust and GF-120 are used for spraying organic cherries. Both products use spinosad, a naturally occurring soil bacterium,GF-120 requires a unique sprayer. It sticks to the tree and insects ingest the insecticide when feeding on the tree. GF-120 can be used for CFFs on home and non-commercial cherry trees. Entrust also controls leafrollers and bud moth larvae (pests for apples) present at the time of application.

References

Alston, Diane. "Optimizing Cherry Fruit Fly Trapping and Evaluation of Insecticides for Fruit Fly Control." Utah State Horticultural Association Convention. 2004. Utah State University Extension System. 20 Nov. 2008.
<http://utahpests.usu.edu/ipm/files/uploads/PPTDocs/04sh-insects-wcffcontrol.pdf>.

"Western Cherry Fruit Fly." Utah Pests Fact Sheet. Nov. 2006. Utah State University Extension System. 20 Nov. 2008. <http://extension.usu.edu/files/publications/factsheet/western-cherry-fruit-flies06.pdf>.

Bessin, Ric. "Cherry Fruit Flies." University of Kentucky Etymology. Jan. 2004. University of Kentucky College of Agriculture. 20 Nov. 2008.<http://www.ca.uky.edu/entomology/entfacts/ef217.asp>.

"Cherry Fruit Fly and Black Cherry Fruit Fly." The Virginia Fruit Page. Virginia Tech Extension System. 20 Nov. 2008. <http://www.virginiafruit.ento.vt.edu/cff.html>.

"GF-120 NF Naturalyte Fruit Fly Bait." Dow Agro Sciences. Organic Materials Review Institute. 20 Nov. 2008. <http://www.certifiedorganic.bc.ca/standards/bnplnotes/GF120%20NF%20Naturalyte%20Fruit%20Fly%20Bait%20E%20Apr06f%20SPECIMEN.pdf>.

Smith, Timothy J. "Organic Cherry Fruit Fly Control with Spinosad (Enrust, GF-120 bait), Compared to a Conventional Provado Standard and an Untreated Check." Washington State University Extension System. 20 Nov. 2008.
<http://www.ncw.wsu.edu/treefruit/documents/2005CFFResultsTJSmithOrganic.pdf>.

"Western Cherry Fruit Fly." North Central Washington Tree Fruit Production. Washington State University Extension System. 20 Nov. 2008. <http://www.ncw.wsu.edu/treefruit/cffartcl_000.htm

"Western Cherry Fruit Fly." Pest Management: Ministry of Agriculture and Lands. June 2006. Government of British Columbia. 20 Nov. 2008. <http://www.agf.gov.bc.ca/cropprot/tfipm/fruitfly.htm>