Agricultural Scientists Ready to Release Parasitic Wasp to Help Prevent Growth of Spotted Wing Drosophila Population

After more than a decade of research, agricultural scientists at Oregon State University are ready to release a parasitic wasp that prevents a highly destructive fruit fly called spotted wing drosophila.

Extension entomologist and Professor Vaughn Walton from the College of Agricultural Sciences said, USDA has authorized the release of the wasp, also known called Ganaspis brasiliensis, a slow process that took 12 years "from application to decision," a Growing Produce report said.

Now that it has a permit, the lab of Walton, which is part of the OSU Agricultural Experiment Station, is raising adequate wasps to make a mark in the spotted wing drosophila population in Oregon.

He said this would have a great impact. He added, that spotted wing drosophila is very difficult to control. It has an extremely high reproduction rate with many generations each year.

Integrated Pest Management Approach

Due to the very high reproduction rate, when using pesticides, they need to be applied constantly, at times, twice, or thrice every week. Growers are quite interested, not to mention excited, about a biological control that will work along with cultural management tools to lessen SWD and not cost them any money.

Essentially, the holistic IPM or integrated pest management approach using cultural controls such as good sanitation, drip irrigation, weed cloth, and proper pruning can be fairly effective.

However, there is still a need for IPM management programs to add pesticides in the fight against spotted wing drosophila, explained Walton.

Spotted wing drosophila is well appropriate for the Willamette Valle climate. Approximately 95 percent live in areas around non-crop habitats that function as pest reservoirs for the crops' reinvasion. That's when and where the wasp will be released.

How the Parasitic Was Kills SWD

In their paper published in Scientific Reports, researchers said the parasitoid wasp kills SWD by laying eggs inside the insect. Then, when the former hatches, its larva eats its prey.

Essentially, spotted wing drosophila populations can be kept at bay at the rate of 65 percent at the most when the parasitoid wasp is around to check it, initial data shows.

Walton said, "We'll never take down the entire fly population." However, he added, as SWD increases, there's more food for the wasp to eat.

Spotted Wing Drosophila

Cornell University describes the SWD as a "vinegar or fruit fly of East Asian origin." It made its way in 2011 to New York. At present, the spotted wing drosophila has spread throughout most of the continental US.

Furthermore, it can directly infect the fruit of various plants, although it is most attracted to blackberries, raspberries, blueberries, and other late-season, soft-flesh fruits, both wild and cultivated.

SWD deserves to be noticed because, different from its relative species, which lay eggs over a ripe or rotting fruit, the fruit fly can lay eggs inside fresh fruits frequently before harvest.

After a couple of days, the fruit skin turns wrinkled or dimpled, forming craters in the fruit. Minus control measures, late-season blackberries, blueberries, and raspberries can suffer upwards of 80-percent loss in crops.

Related information about the spotted wing drosophila is shown on The Ohio State University IPM Program's YouTube video below:

Check out more news and information on Wasps in Science Times.