Spotted-wing drosophila

Drosophila suzukii

55 host plants

Last updated

Spotted-wing drosophila (Drosophila suzukii) damages ripe-to-overripe berry and stone fruit by depositing eggs directly beneath the skin. Larvae tunnel through fruit tissue creating brown, sunken areas; infested fruit develops a fermented or sour smell as bacteria from egg-laying females contaminate the fruit. Berries like raspberry, blackberry, and blueberry are particularly susceptible.

Monitor ripe fruit starting in June for collapse signs. Harvest fruit promptly when ripe rather than leaving it overripe. Exclude flies with fine-mesh netting. Remove fallen fruit promptly. Spinosad and pyrethrin-based products provide good control with low residue concerns.

Quick Reference

Order
Diptera
Type
piercing-insect
Host Plants
55
Peak Activity
Year-round in WA; peaks spring and fall; trap-based monitoring
Damage Severity
growth-reducing
Now: Spring ReactivationModerate Risk

Overwintered adults resume activity as temperatures consistently exceed 50°F. Early generations develop on wild hosts (elderberry, honeysuckle) before cultivated fruit ripens. Population building but damage not yet occurring on crops.

Next: Fruit Vulnerability Window Seasonal guidance →

Monitoring & Action

How to Monitor

Apple cider vinegar traps: fill a container with ACV plus a drop of dish soap, punch 3/16-inch holes in the lid. Deploy traps in late May before fruit ripens. Check weekly. Male wing spots confirm SWD presence (vs. common vinegar flies). Replace bait every 1-2 weeks.

When to Act

Any male SWD caught in monitoring traps when susceptible fruit is coloring warrants protective action. Zero-tolerance in commercial settings. In home gardens, trap catches trigger harvest frequency increase and netting deployment.

What Damage Looks Like

Females lay eggs singly inside ripening (not overripe) fruit through punctures made by the serrated ovipositor. Larvae feed internally, causing soft spots, collapse, and secondary fungal infection (Botrytis, Rhizopus). Infested fruit often appears normal externally until larvae are well developed. A single female can lay 300+ eggs over her lifetime. Harvest losses can exceed 60% in unprotected plantings. Oviposition scars (small breathing holes) are sometimes visible as pinprick marks on the fruit surface.

Cultural Controls

  • Exclusion netting (<1mm mesh) deployed after pollination, before fruit colors; most effective home garden control (Cornell: 0.37-0.53% infestation vs 60% without)
  • Harvest frequently (every 2-3 days when fruit is ripe); do not leave ripe fruit on bushes
  • Remove and destroy fallen fruit immediately; compost piles must reach 130°F+ to kill larvae
  • Refrigerate harvested fruit promptly (below 40°F stops larval development)
  • Prune to maintain open canopy for air circulation and faster fruit drying

Host Plants (55)

Arbutus unedo Strawberry Tree, Killarney Strawberry Tree, Madroño Betula lenta Sweet Birch, Cherry Birch, Black Birch Cornus capitata Evergreen Dogwood, Bentham's Cornel, Himalayan Strawberry Tree Euonymus americanus American Euonymus, Hearts-a-Burstin', Strawberry Bush Fragaria × ananassa Garden Strawberry Fragaria chiloensis Beach Strawberry Sand Strawberry, Chilean Strawberry Malus robusta Cherry, Crabapple Microcachrys tetragona Creeping Pine, Creeping Strawberry Pine Prunus americana Wild Plum American (Red) Plum August Plum, Goose Plum Prunus armeniaca Apricot Prunus avium Sweet Cherry Prunus besseyi Sand Cherry, Western Sand Cherry Prunus blireiana Blireiana Plum Prunus caroliniana Carolina Cherrylaurel American Cherrylaurel Prunus cascade Prunus cascade Prunus cerasifera Cherry, Plum Prunus cerasus Sour Cherry Prunus cistena Purpleleaf Sandcherry Redleaf Sandcherry Cistena Sandcherry Cistena Plum Prunus dream Prunus dream Prunus emarginata Bitter Cherry, Wild Cherry, Quinine Cherry Prunus first Prunus first Prunus fruticosa Steppe Cherry, European Dwarf Ground Cherry, Mongolian Cherry Prunus glandulosa Dwarf Flowering Almond Prunus ilicifolia Hollyleaf Cherry, Holly-leaved Cherry Prunus laurocerasus Cherry Laurel Prunus lusitanica Portugal Laurel Prunus maackii Amur Chokecherry Amur Cherry, Manchurian Cherry Prunus mume Japanese Flowering Apricot Prunus newport Newport Flowering Plum Prunus okame Okame Flowering Cherry Prunus padus European Birdcherry Common Birdcherry Prunus prostrata Rock Cherry, Mountain Cherry Prunus sargentii Sargent Cherry, Sargent's Cherry Prunus serotina Black Cherry, Rum Cherry Prunus serrula Birchbark Cherry, Paperbark Cherry, Tibetan Cherry Prunus serrulata Japanese Flowering Cherry Prunus snow Prunus snow Prunus subcordata Klamath Plum, Sierra Plum, Pacific Plum Prunus subhirtella Higan Cherry Prunus subhirtella var. autumnalis Autumn Flowering Higan Cherry Prunus tai Prunus tai Prunus virginiana Prunus virginiana Prunus virginiana var. demissa Western Chokecherry Prunus virginiana var. virginiana Common Chokecherry, Eastern Chokecherry Rubus allegheniensis Allegheny Blackberry Rubus armeniacus Himalayan Blackberry Armenian Blackberry Rubus calycinoides Crinkle-leaf Creeper Creeping Raspberry Yü-shan raspberry Rubus dicolor Himalayan Blackberry Armenian Blackberry Rubus idaeus Red Raspberry Rubus laciniatus Evergreen Blackberry Cutleaf Blackberry Rubus leucodermis Blackcap, Western Raspberry Rubus odoratus Flowering Raspberry Purple-flowering Raspberry Rubus tricolor Creeping Bramble Korean Raspberry Rubus ursinus Trailing Blackberry Western Blackberry California Blackberry Dewberry Waldsteinia fragarioides Barren Strawberry

SWD is well established throughout the Puget Sound lowlands and is one of the most damaging fruit pests in home gardens. The maritime climate with moderate summer temperatures (70-80°F) is ideal for SWD - populations build faster here than in hot-summer regions where temperatures above 86°F suppress reproduction. First detected in western Washington in 2009. Trap monitoring should begin in late May. Blueberries, raspberries, and cherries are the most commonly affected home garden crops. Exclusion netting is the most effective non-chemical option for home gardeners.

— Chris Welch, ISA Certified Arborist

Sources & References

Primary: PNW Insect Management Handbook

  • WSU HortSense
  • UC IPM Pest Note 74158: Spotted-wing drosophila
  • Wiman et al. (2014) OSU: SWD temperature biology and seasonal activity
  • Asplen et al. (2015) J. Pest Science: Invasion biology of spotted wing Drosophila
  • Cornell netting economics study 2024
  • Girod et al. (2022): Ganaspis kimorum approved for US release
Data Maturity
Structured Multiple sources. Expert review underway.