Multiple Methods for Fighting Spotted Wing Drosophila

Researchers are investigating new behavioral and cultural controls to help protect crops from spotted wing drosophila (SWD).

SWD has been attacking many crops, such as small berries, and leaving growers with devastating losses, said Ashfaq Sial, assistant professor at the University of Georgia. This pest is such an issue for growers because there is a very large window of when the crop is susceptible. As soon as the fruit begins to ripen, SWD can lay eggs in the fruit, making it unable to be placed into the market.

Sial said researchers, including himself, have been studying control methods that allow growers to use fewer chemicals than they would typically need. The first type of these methods is using traps.

Placing traps in fields can allow growers to find out what kind of pests and population densities are present in their crops. However, traps do not typically help with eradicating the SWD. What the traps do is help growers detect the pests before they have done major damage to the crops. This preemptive measure can help reduce the damage caused by the pests by enabling growers to implement control tactics before significant damage occurs. Traps can also help growers figure out what type of management plan they will need against SWD.

One behavioral control method currently being tested involves leading the SWD to a ball-like device which is filled with attractant and a small amount of pesticide. Sial said the pest is attracted to this device with the intention of feeding. SWD will pick up some of the insecticide from the device, which will then kill the pest. The devices are placed around the perimeter of the field approximately 2 to 3 meters apart from one another, attracting the pests away from the crops.

Researchers are also studying cultural controls to prevent SWD. Sial said the first step is pruning more of the crop than a grower typically would. This allows more sunlight and heat into the canopy, which can create an inhospitable environment for the SWD.

Various mulches have also been studied to help prevent the adult SWD from developing in the crop. By using black weed mats, growers have been able to prevent the larvae from maturing, by blocking their ability to burrow into the ground to mature. The color of the mat is important because black mats absorb more sunlight, also creating an environment incapable of housing SWD.

Netting to exclude SWD from the crop has also been used as a highly effective method for protecting small production systems. In a test completed, Sial said the crops inside the netting system were found to have no SWD. In a control set up near the netting system, the rate of SWD was more than 80 percent in the crop.

This difference in these levels shows growers and researchers that netting would be a viable option to protect crops efficiently. However, this technique would not be possible for large production systems because of the need to cover the entirety of the crop and associated costs.

This research was conducted as part of a multi-regional project sponsored by the Organic Agriculture Research and Extension Initiative from the United States Department of Agriculture’s National Institute of Food and Agriculture.