Drosophila suzukii control: Preventive measures in organic stone fruit orchards

Summary

The combination of preventive measures and intervention measures can reduce D. suzukii puncture and/or the development of larvae inside the fruits, and therefore minimise fruit and economical losses.
Practical recommendation
• Monitoring: Once the fruits begin to change colour from yellow to red until harvest, monitor D. suzukii presence weekly using bait traps. Mount monitoring traps in shady, protected places and check weekly during the flight season from April until the end of the harvest. Males can be identified by dark wing spots visible to the naked eye. In females, the large, curved ovipositor with well-developed, dark saw teeth can be seen with a magnifying glass.
• Fruit inspection: Inspect 50 externally intact random fruits with a magnifying glass. Check for egg deposition and puncture holes, and egg deposition with typical egg filaments that stand out from the fruit.
• Orchard management (+++): D. suzukii likes humid, shady, wind-protected locations. Dry and hot weather is unfavourable. Implement measures that lead to a dry orchard climate. Choose pruning sys-tems that ensure a well-aerated, rapidly drying stand; mulch the undergrowth frequently or lay black mulch film; adjust irrigation intensity to avoid puddles.
• Hygiene and harvest (++): In case of high infestation pressure, harvest all cherries in one cycle (and dispose of the unripe fruits), as the second harvest cycle is usually heavily infested and often no longer marketable. Completely harvest early varieties, remove and destroy overripe and damaged fruit (put them in an airtight container) to avoid a D. suzukii proliferation. Immediately cool the harvested fruit to 0-3 °C to stop larval development. Keep the cold chain until delivery to consumers.
• Choice of cultivar (+): There are some cultivar differences for apricots and plums, while with cherries all varieties are attractive.