Western cherry fruit fly

Cherry Fruit Flies (Western, Black)

General Description


Sweet and sour cherry, bittercherry (Prunus emarginata), Mahaleb cherry (P. mahaleb)


Larvae (maggots) feed in the flesh near the pit of cherries rendering them unmarketable. Larvae do not produce pellets of frass like the cherry fruitworm which also feeds around the pit.


Larva – White, legless maggot with no head capsule; about 5-6 mm long when mature (Fig. 1).

Figure 1. Western cherry fruit fly larva feeding in sweet cherry. (H. Philip)

Pupa – About 4-5 mm long, gold to brown colour, elongate-oval shape.

Adult- Slightly smaller than house fly, black body with yellow markings near base of wings and white stripes across abdomen. Wings have black markings, which are used to identify these pests from related fruit flies (see images of wings).

Figure 2. Wing patterns of the Western (top) and Eastern (bottom) cherry fruit fly. Figure 3. Wing patterns of the Black cherry fruit fly(top) and the Walnut husk fly (bottom).
Figure 4. Wing patterns of the Apple maggot/Snowberry maggot (top) and Currant fruit fly (bottom).

Life History

Cherry fruit flies overwinter as pupae in the top 2-5 cm of soil under cherry trees. Adults are present from late May into August, generally peaking from early to mid-July, depending upon location. Black cherry fruit fly adults begin emerging 1-2 weeks before western cherry fruit flies. Five to 9 days after emerging, female flies lay eggs singly in cherries and larvae feed for 1-2 weeks around the pit before cutting exit holes and dropping to the ground to pupate. There is only one generation each year; 3-4% can have a second generation in August and a similar proportion can overwinter for 2 or more years.


Traps are useful in determining first emergence of cherry fruit fly, particularly on a regional basis (Fig. 2). Trapping results should not be relied on to determine whether control sprays are needed. Yellow sticky traps are not very efficient for detecting fruit flies, especially when numbers are low, such as in well-managed commercial blocks. Hang traps in an area where flies are most likely to be caught; local neglected or abandoned trees within a kilometer of commercial orchards, or in difficult to spray areas of cherry blocks. Placing traps where there is a known high population of fruit flies is more important than the number of traps.

Figure 2. Yellow sticky trap.

Use commercially available yellow sticky traps baited with ammonium carbonate to increase attractiveness. Rebell™ traps are more attractive than other types of yellow sticky traps. Hang traps by mid-May at eye-level in exposed sunny parts of the trees. To prevent debris from collecting in the trap clear all the leaves and twigs for 40 cm around each trap. Check traps daily until the first flies are caught.

Outside unmanaged sources are a common threat to most growers, it is therefore important to monitor borders nearest these sources. This will ensure early detection of flies entering the block and timely application of protective sprays to prevent establishment and spread. In the presence of cherries, 90% of adults will not travel beyond a short distance, but some can fly up to 500 m or more.


Cultural Control

At the time of cherry bloom, search out and destroy any unmanaged hosts within a distance of at least 250 m of the orchard. Destroy infested fruit before the larvae emerge.

Chemical Control

The low efficiency of yellow sticky traps and zero tolerance for fruit flies in fruit requires protection of the fruit throughout the summer when fruit flies are active, regardless of trapping results. If using traps, apply a control product within 5 days of first fly capture and maintain control until harvest in a given region, usually early to mid June. Maintain control until all the fruit is removed or completely shriveled on the trees. In the absence of traps, begin protecting fruit about the time Lambert cherries begin to colour. Research shows female fruit flies will lay eggs in green fruit. This means application of sprays to the new later maturing varieties when the fruit may still be green.

The following table presents information on recommended control products.

NOTE: If your cherries are destined for foreign markets, check with your packinghouse, crop certifier or broker to confirm which spray products can be applied to cherries entering the country (MRL present) or allowed by the buyers. Do not risk fruit infestations by exceeding the spray intervals. Re-apply the products after any measurable rain event to ensure fruit flies are exposed to lethal residues.

Trade Name

Common Name

Target Stages

Maximum Number of Applications

Spray Interval1


Pre-harvest Interval (days)

Admire 240F2

or Alias 240 SC2


Larvae, adults

Assail 70 WP2



Cygon 480 or Lagon 480 E


Larvae, adults

Delegate (suppression only)







5 – 7




Harvanta cyclaniliprole Adults 3 7 7




1 Minimum days between sprays when applied at recommended rates in absence of rainfall or overhead irrigation

2 Minimize use to avoid mite problems.

Exirel, Entrust 80 W and GF-120 sprays will only control adult fruit flies. Delegate will only provide suppression. Apply the first spray not later than 5 days after capture of the first fly followed by sprays at recommended intervals to maintain protection of fruit to harvest.

Entrust and GF-120 are approved for use in organic cherry blocks. Both products contain spinosad. Entrust will also control leafroller and bud moth larvae present at the time of application. GF-120 requires a special sprayer which can be purchased or fabricated – do not use an air-blast sprayer. Carefully read the label instructions before mixing and applying GF-120. Because GF-120 does not control other insect pests (such as cherry fruitworm, leafrollers, aphids, spotted wing drosophila), growers should monitor for the presence of other pests to determine need for control. To prevent damage by other insect pests, consider applying fruit fly control products that also provide protection against other major pests present (for example, Admire, Alias, Cygon or Exirel for aphids; Delegate for cherry fruitworm, leafrollers; and Delegate, Exirel or Cygon for spotted wing drosophila).

Admire and Alias have some residual contact activity against adult flies (2-3 days) but will kill young larvae hatching in the egg for 10 to12 days post treatment because it is absorbed into the fruit. These products will also move into the branches and out to the growing tips where it will control any black cherry aphids present. Some research shows mite populations increase after neoticotinoid products such as Admire/Alias or Assail are applied. Therefore do not use Admire/Alias or Assail more than twice per season. Avoid use of any chemicals harmful to predatory mites in blocks treated with Admire/Alias or Assail to avoid possible mite flare-up. Monitor mites the following spring to assess the risk of mite problems.

Because Cygon and Lagon may not protect the fruit up to harvest, an additional application of another product may be required. Be aware of the preharvest intervals. For sour cherries, do not apply Cygon or Lagon more than twice per season. Apply the second spray 21 days after the first.

A very important application is a post harvest spray of Admire or Alias (if either only used once before), Cygon or Lagon to prevent late-emerging fruit flies breeding in unharvested whole or split cherries.

Field reports indicate control products formulated as emulsifiable concentrates (EC) can cause severe leaf burn and possible drop in Lapin, Sam, Stella, and Sweetheart cherry varieties. Also, some leaf burn and drop may occur if GF-120 is applied to undersides of leaves.

by Frank J. Messina and Timothy J. Smith, originally published 1993; revised August 2010

Rhagoletis indifferens Curran (Diptera: Tephritidae)

Cherry fruit fly adult (E. Beers, June 2007)

The western cherry fruit fly is a key pest in all cherry growing regions of the western United States. It is native to North America and was reported attacking commercial cherry in the Pacific Northwest in the early 1900s. It was found in the Yakima Valley in 1942 and the Wenatchee area in 1950.

The fly’s larva develops in ripening cherries. If uncontrolled, the pest can ruin almost all the fruit on a tree. Even poor control can have serious consequences since major markets for Northwest cherries, such as California and many foreign countries, do not tolerate any infestation of packed cherries.

Adults are weak migrators and will travel no further than necessary to find a host tree. For this reason, infestations in a region tend to be spotty. However, infestations within an orchard, where the trees are close together, can spread rapidly.


Cherry fruit fly attacks all varieties of cultivated and wild cherries.

Life stages


The egg is yellowish and elongated with a stalk at one end. It is about 1/30 inch long (0.8 mm) and is deposited under the cherry skin.


The larva is a creamy white, legless maggot, which is tapered at the head and blunt at the rear. It passes through three instars and grows to about 5/16 inch (8 mm) long. Maggots found in cherries may be those of the cherry fruit fly or could also be larvae of the family Drosophilidae. The Drosophila fruit flies do not attack fruit unless the skin has been physically damaged, allowing an opening for deposition of eggs. (NOTE: this generalization has changed with the arrival of spotted wing drosophila, Drosophila suzukii, which CAN attack undamaged fruit before it is fully ripe.) This usually happens when cherries are cracked because of wind or rain damage or bird feeding or are decayed. Larvae of the cherry fruit fly, and other Rhagoletis species, can be distinguished from the Drosophila species by examining the posterior end of the larvae. The posterior end of the cherry fruit fly larva is rounded and the anal spiracles, which are not raised, each have three darker lines extending laterally from the mid-line. The posterior of Drosophila larva has two protuberances on which the anal spiracles are found.


The pupa is yellowish brown to dark brown and looks like a large grain of wheat. It is about 3/16 inch (4 mm) long.


The adult has a black body with white bands on the abdomen. The wings are transparent with a distinctive dark banding pattern. It can easily be distinguished from other fruit flies by the wing pattern. The fly is about 1/5 inch (5 mm) long. The female is slightly larger than the male.

Western Cherry Fruit Fly Info – Controlling Western Cherry Fruit Flies

Western cherry fruit files are small pests, but they do big damage in home gardens and commercial orchards across the western United States. Read on for more western cherry fruit fly information.

Western Cherry Fruit Fly Identification

Western cherry fruit flies live in the soil as brownish-yellow pupae during the winter months, emerging as adult flies in late spring and early summer. Adult western cherry fruit flies are smaller than house flies, with black bodies marked with white bands. The flies are weak fliers and usually land on the nearest cherry tree.

Female western cherry fruit flies, which fatten up on aphid honeydew and pollen, are ready to lay eggs about a week after emerging from the soil. Females live 35 days or less, but this relatively short period of time is long enough to do serious damage, which the pests accomplish by poking holes and laying eggs inside cherries.

One female can lay 50 to 200 eggs, which hatch maggot-like larvae in five to eight

days. The larvae burrow deep into the cherry where they feed and grow for 10 to 12 days before falling to the ground, where the cherry fruit fly life cycle begins again.

Western Cherry Fruit Fly Control

In home gardens, fine netting can prevent adult fruit flies from landing on ripening fruit. Drape the netting over the tree and secure it with string or tape. Leave the netting in place until you’re ready to harvest the cherries.

While netting is effective for single trees, insecticides may be the best way of controlling western cherry fruit flies in orchards. The key to using insecticides effectively is timing. Many orchardists use baited sticky traps that reveal when adult flies are active – usually in mid-spring, when cherries are light green.

Several insecticides have proven to be effective in cherry fruit fly control, including spinosad, carbaryl, malathion and permethrin. Contact your local Cooperative Extension Office for specific info for controlling western cherry fruit flies in your area, as timing is critical. Use insecticides with care, as improper use may kill beneficial insects, including honeybees.

Preventing and Controlling Western Cherry Fruit Flies

Here are some tips that can help with prevention and control of these pests:

  • A thick layer of mulch on the ground around cherry trees may prevent the pests from burrowing into the soil, thus limiting new hatches.
  • Avoid leaving cherries on the trees at the end of the season to ensure the removal of all pest-infested fruit. If necessary, prune trees so you can easily reach the fruit. Similarly, pick up all fruit that drops on the ground. Insecticides may be needed to control late-emerging flies.
  • Parasitic wasps – especially braconid wasps – can help control the pests in home gardens, but usually aren’t effective in orchards.

Cherry-Western cherry fruit fly

Rhagoletis indifferens

Pest description and crop damage Adults are somewhat smaller than a house fly. They have brownish to black wings with dark bands. White maggots infest cherries. The mature maggot makes a hole in the cherry as it exits. In the Northwest, the western cherry fruit fly is known to infest both home grown and commercial cherries. Western cherry fruit fly is also found in wild bitter cherry (Prunus emarginata).

Biology and life history The flies overwinter as pupae in the soil. The adult flies emerge from the soil from mid May, about 5 weeks before harvest, until the end of July. Peak emergence often coincides with harvest. Adults feed on honeydew on leaves and pollen. After 7 to 10 days, females lay eggs under the skin of the fruit. The eggs hatch, and the larvae burrow toward the pit of the fruit. There they feed for 10 to 21 days before boring out and dropping to the ground to pupate. There is one generation per year. Adults emerge early the following season. A few pupae of western cherry fruit fly may remain in soil as long as 3 years.

Pest monitoring There is no tolerance for cherry fruit fly in cherry fruit, thus the threshold is zero. Degree day models are used to determine first emergence in the major cherry production regions of the Pacific Northwest. Consult with your county Extension agent to determine the development of cherry fruit fly populations in your area. Yellow sticky traps hung in sunny parts of the tree will attract adults. Monitor daily.

Management-cultural control

Home orchardists: Grow early-maturing varieties such as ‘Chelan.’ Pick fruit within 8 to 9 days of catching the first flies, which will happen before egg hatch. Remove all fruit from the trees to eliminate sites for the fly to reproduce. Cultivation of the soil has not been effective, as the pupae are very hard-shelled.

Management-chemical control: HOME USE

Warning: Many pesticides are hazardous to bees. Look for bee precautionary statements on product labels and do not use these products during bloom or if bees are foraging in the orchard.

Begin spraying late May and continue through harvest. Spray at 10 to 21 day intervals. Degree-days can also be used to better determine fly emergence which is 950 degree-days after March 1.

  • acetamiprid
  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • kaolin clay (Surround at Home)-Applied as a spray to leaves, stems, and fruit, it acts as a repellant to some insect pests. OMRI-listed for organic use.
  • permethrin
  • pyrethrins-Some formulations are OMRI-listed for organic use.
  • spinosad-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

Warning: These materials are hazardous to bees. Do not use during bloom or if bees are foraging in the orchard.

Growing-season sprays

  • acetamiprid (Assail 70WP) at 2.3 to 3.4 oz/a. REI 12 hr. PHI 7 days.
  • carbaryl (Carbaryl 4L) at 2 to 3 quarts/a. REI 12 hr. PHI 3 days. Extremely toxic to aquatic invertebrates; avoid spray drift and runoff to surface waters.
  • diazinon (Diazinon 50W) 4 lb/a. REI 4 days. PHI 21 days. Do not exceed one in-season application per year.
  • esfenvalerate (Asana XL) at 4.8 to 14.5 fl oz/a. REI 12 hr. PHI 14 days. May aggravate spider mite problems. Extremely toxic to fish and aquatic invertebrates; avoid spray drift and runoff to surface waters.
  • imidacloprid (Provado 1.6F) at 6 to 8 fl oz/a. REI 12 hr. PHI 0 days. Do not use until pollination is complete and bees are no longer present.
  • malathion (Malathion 57EC) at 1 pint/a. REI 12 hr. PHI 3 days. May injure certain varieties of sweet cherries. Malathion sprays may be less hazardous to bees.
  • malathion (Fyfanon ULV Ag) at 16 oz/a. REI 12 hr. PHI 1 day. Not a stand-alone product for SWD control. Do not use sequential sprays for SWD control. Maximum applications per season: sweet cherries- 4; tart cherries- 6. Repeat treatments after heavy rain if label allows.
  • spinetoram (Delegate 25WG) at 6 to 7 oz/a. REI 4 hr. PHI 7 days. Maximum four applications per season.
  • spinosad-
    • Entrust SC at 4 to 8 fl oz/a. REI 4 hr. PHI 7 days. OMRI-listed for organic use.
    • Spinosad bait (GF 120 NF) at 20 fl oz/a. REI 4 hr. No PHI listed. Apply every 7 days. Apply immediately upon first emergence. Can be applied by air or with an all-terrain vehicle. Apply 0.8 to 1 gal/a with a D2 nozzle (without a core) attached to an ATV traveling at 6 to 7 mph. OMRI-listed for organic use.
    • Success 2F at 4 to 8 fl oz/a. REI 4 hr. PHI 7 days. Do not exceed 29 fl oz/a per year.
  • thiamethoxam (Actara 25WDG) at 4.5 to 5.5 oz. REI 12 hr. PHI 14 days. Repeated applications may cause spider mite buildup. Do not exceed 11 oz /a per season.

Postharvest spray

  • dimethoate (Dimethoate 4E) at 1 quart/a. REI 10 days (REI 14 days in areas with less than 25 inches/year). One post-harvest application permitted in Oregon, Idaho, and Washington. Do not feed or graze livestock on cover crops in treated orchards. Do not mix with Syllit.

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