Cherry fruit fly

About

Small flies, a bit smaller than a housefly, with dark bands on their wings. Their creamy white maggots, up to 5/16 inch long, feed inside cherries.

Spotting it

Damage

Infested cherries are shrunken and misshapen, ripen early and have exit holes where maggots left. The maggots are much larger than spotted wing drosophila larvae.

How to find it early

Hang yellow sticky traps with an ammonium lure in the canopy, clearing leaves and fruit 12 to 18 inches around each one (Penn State). Watch for adults from May to mid-July in Utah.

When

Late spring through midsummer; western cherry fruit fly peaks around harvest (WSU).

Life cycle

There is one generation a year. Maggots burrow a few inches into the soil to pupate and spend winter there; adults emerge from late spring into summer, and females lay eggs under the skin of ripening fruit for three to four weeks.

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Pick every cherry, and deal with neglected trees Prevent

   WSU says few flies finish their life cycle if all fruit is picked and removed early in the harvest period. Removing unmanaged cherry trees nearby cuts the local population.

2. Yellow sticky traps for timing Trap

   Use traps with an ammonium lure to see when flies first appear. Penn State starts protection about a week after the first fly is caught.

   Traps show timing; they do not control the fly.

3. Spinosad fruit-fly bait Organic spray

   WSU calls spinosad bait (a sugar bait with a small amount of spinosad) very effective and practical on home cherry trees, with a 0-day pre-harvest interval on its label.

   Spinosad is toxic to bees for a few hours to a day (PNW 591); do not apply during bloom. Follow the label.

4. Carbaryl, malathion, esfenvalerate or permethrin Conventional spray

   USU lists these for home cherry trees, applied from first fly catch through harvest at the label interval.

   All are highly toxic to bees (PNW 591): never spray during bloom. Carbaryl has been a restricted-use pesticide in California since August 1, 2020 (UC IPM), so California home gardeners cannot buy it without an applicator license. USU notes not all products are registered for edible crops: check that cherry is on the label and follow the pre-harvest interval.

Plants it goes after

Cherry (sweet and tart), Nanking cherry, Pear, Plum

Pressure by region

The eastern species is sourced for Pennsylvania; the western species has been in the Pacific Northwest since the 1940s (WSU) and is a pest in Utah (USU). The Midwest rating, and the low ratings elsewhere, are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.