Awareness Key In Grounding Spotted Wing Drosophila’s Aerial Assaults
September 23, 2015 The spotted wing drosophila (SWD), Drosophila suzukii Matsumura, is the most serious threat to the Florida blueberry industry. During the 2015 production season, approximately 90% of the blueberry plantings surveyed were infested with SWD.
The maggot (larva) develops inside the berry by feeding on the soft tissues making it impossible to market the fruit. SWD was first recorded in Florida in 2009 and since that time has spread to more than 28 counties within the state.
The fly is different from other vinegar fruit flies that infest overripe, rotting, and decaying fruits, choosing to lay its egg in ripe or ripening intact fruit instead.
Annual losses as a result of SWD in Florida blueberry plantings is estimated between $10 million to $15 million. This type of loss is substantial for a small industry like blueberry, which reports annual sales between $60 million to $70 million.
Cooperation Needed
It is becoming increasingly obvious that areawide pest management strategies are the most effective approach to managing SWD populations in blueberry plantings. Areawide pest management requires the full cooperation of all the growers in a particular area that grow small fruits, which SWD usually target and invade.
All of the growers are required to carry out the basic management tactics for this fly that include monitoring, coordination, rotation of sprays, and regular harvesting of fruit. It also is recommended that management tactics be extended to other hosts including wild fruits that the fly is capable of invading.
In Florida, hosts such as wild blackberry (Rubus spp.), nightshade (Solanum spp.), wild blueberry Vaccinium spp. and holly (Ilex spp.), are abundant in unmanaged areas adjacent to blueberry plantings and can influence the population of SWD in the crop.
Monitoring for SWD larvae should be conducted weekly using ripe fruit. The number of samples depends on the size of the field and whether there is a high risk of infestation. Too few samples may miss an infestation. Growers should randomly pick 100 to 200 berries every 5 acres and samples should be collected from the field borders and the center of the field. Crushing berries and placing them into a container with concentrated salt or sugar solution (20%) will cause maggots to float to the surface if berries are infested.
♦ Scientist Has Sights On Shooting Down SWD ♦
Alternatively, adult flies can be monitored using transparent cups (traps) with small ¼-inch holes to allow flies to enter. These cups should be baited yeast/sugar solution. Traps should be checked at least once per week.
Taking Control
Chemical applications should be based on monitoring data obtained from traps or larval counts from berries. Once SWD is recorded in the planting, the grower should embark on a spraying program and aim at a 10- to 14-day cycle. However, if infestation is high, this cycle should be shortened to 7 to 10 days.
Growers should use selective insecticides to decrease the impact on beneficial insects, including bees. Insecticide should be rotated between different classes to delay the onset of resistance. Growers should always follow the label and use products with short postharvest intervals when in the middle of the harvesting period.
Regular harvesting of ripe berries also is critical as it provides less resources for flies to lay their eggs.
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