(Beyond Pesticides, December 12, 2019) A breakthrough study in biological pest management has found a species of wasp can, when combined with other non-toxic methods, readily replace toxic pesticide use in the management of the invasive spotted-wing drosophila (SWD). SWD is a fruit fly originally from southeast Asia that has caused significant crop losses in the U.S. over the last decade, estimated at over $700 million each year. The success of this integrated biological approach underlines the importance of public funding for non-chemical methods of pest management.
SWD looks like any other fruit fly, laying its eggs in fruit that subsequently hatches maggots, which feed on and ruin the fruit. It has been particularly virulent and damaging in the U.S. due to a lack of natural predators. Scientists at Oregon State University tested the viability of the parasitic wasp Pachycrepoideus vindemmiae to manage SWD because it is one of very few species found to kill SWD under field conditions. The parasitoidâ€™s pest-management capacity was investigated by identifying the resources required to keep it alive, and how the provision of resources affected its host-killing potential
P. vindemmiae performed well as a SWD control agent due to its ability to life quite long under both limited and ample resources, with ample resources enhancing its ability to manage the pest. Providing constant water and honey resulted in wasp survival upwards of 70 days without any host, indicating an ability to rear and maintain populations outside of an infested site. Researchers saw no impact of resource limitation on P. vindemmiae egg hatching. Even wasps that were completely starved after birth were able to live over 10 days. This is significant as other studies of different SWD parasitoid species have found live spans that rarely reach one week.
A single wasp is able to kill up to 600 SWD throughout its lifespan. â€śBased on the survival and host-killing capacity of the wasp, we have concluded that it has tremendous biocontrol potential against SWD,â€ť said Vaughn Walton, PhD, professor at OSUâ€™s College of Agricultural Sciences in a press release.
The parasitic wasp has the potential to replace a conventional approach that prescribes pesticide dependency. “Spotted wing drosophila is very difficult to control,” said Dr. Walton. “It’s got a very, very high reproduction rate, many generations a year. Because of that, when using pesticides, they have to be applied constantly, sometimes two to three times a week.”
But even the wasp itself will not be effective unless other cultural best practices are followed, including the use of drip irrigation, proper sanitation, and weed cloth barriers that prevent SWD from infesting the soil after dropping to the ground on a pest-ridden piece of fruit.
“The wasp helps, but you must do the other things as well,” Dr. Walton said. “None can stand on its own. If you’re doing all of the cultural practices, you’re going to have a much lower problemâ€¦ Even removing one [pesticide] application is a significant cost savings â€“ $150 an acre. That’s a lot of savings if you can do all of these things together.”
This research took place under the U.S. Department of Agricultureâ€™s Specialty Crop Research Initiative, a project aimed at regional management of SWD in California and the pacific northwest. The success of this approach underlines the importance of spending public monies on research into non-chemical means of pest management. Use of P. vindemmiae would not only save farmers money by saving crops; theyâ€™ll save on the cost otherwise spent on toxic pesticides, which could additionally cost farmers and farmworkers money in the form of future health care necessitated by pesticide-induced diseases.
Individuals wishing to eliminate the use of toxic pesticides in their own homes and yards can turn to Beyond Pesticidesâ€™ ManageSafe portal for non-toxic management approaches that work on a range of indoor and outdoor pests.
All unattributed positions and opinions in this piece are those of Beyond Pesticides