The Wayne County Extension integrated pest management (IPM) scouting program regularly monitors for the presence of the Spotted Wing Drosophila (SWD) fruit fly on several area commercial fruit farms. In late June, SWD were identified in several traps.
The SWD is an economical threat to fruit producers and reduces the marketability of fruit. The presence of SWD in out area indicates that fruit growers, especially those who produce any kind of raspberries, blackberries, blueberries or grapes need to take preventative action as those fruit crops begin to ripen.
Unlike the common fruit or vinegar flies that are a pest of over-ripe fruit, the SWD is able to damage fruit as it starts to ripen. Each female fly can lay between 300 to 350 eggs. Under optimum conditions, the lifecycle from egg to adult can be completed in eight to ten days and there are multiple generations per year. Without preventative treatment, numbers can quickly build to high levels, making that fruit generally un-marketable.
At this point, the only reliable method for a high degree of control is the use of chemical insecticides applied on a regular and consistent spray schedule. Thorough spray coverage is essential for good control, from the top to the bottom of the plant and spray needs to penetrate into the plant canopy. In addition to the use of insecticides, damage by SWD can be minimized by storing fruit at cold temperatures as soon after picking as possible. Research indicates that fruit quality is maintained and cold storage can produce mortality of both mature larvae as well as eggs. Sanitation also plays a role in control and reducing the number of SWD.
Home gardeners and commercial fruit producers alike are encouraged to rotate between chemical classes to reduce the possibility of chemical resistance developing in the SWD population. More information about the SWD and its lifecycle, along with a chart of labeled and approved insecticides used to control the pest and timing of insecticide applications can be found at http://u.osu.edu/pestmanagement/pests/swd/ or contact the Wayne County Extension office at 330-264-8722.
A salt-water test provides a quick diagnostic to determine if SWD have infested fruit. Details on how to perform the salt-water test are available at the previously mentioned web site.