Cherry Fruit Flies (Western, Black)


General Description

Hosts

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

Damage

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.

Identification

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.

Monitoring

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. 

Management

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

(days)

Pre-harvest Interval (days)

Admire 240F2

or Alias 240 SC2

imidacloprid

Larvae, adults

2

10

7

Assail 70 WP2

acetamiprid

Adults

2

12

7

Cygon 480 or Lagon 480 E

dimethoate

Larvae, adults

1

14

21

Delegate (suppression only)

spinetoram

Adults

3

7

5

Entrust

spinosad

Adults

4

5 - 7

7

Exirel

cyantraniliprole

Adults

4

7

3

Harvanta cyclaniliprole Adults 3 7 7

GF-120

spinosad

Adults

10

7

0

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.