Oklahoma Farm Report intern Haden Snelson sat down with Justin Talley, head of Oklahoma State University’s Department of Entomology and Plant Pathology, at the Oklahoma Cattlemen’s Association Convention and Trade Show to discuss the latest efforts to prevent New World screwworm from reaching Oklahoma.
“Right now, there is a concern with any type of animals moving that could move this fly into Oklahoma,” Talley said. “But looking at the movement and how it’s progressing through Texas, we have high confidence that the sterile insects are working.”
New World screwworm larvae feed on the living tissue of warm-blooded animals after female flies lay eggs in wounds. Infestations can cause severe injuries and death if they are not quickly identified and treated.
Talley said millions of sterile flies are being released in Texas following confirmed infestations. The flies may be distributed by aircraft or through ground releases near detection sites.
“They’ve done an amazing job because, as you see the progression of this move, it’s not a rapid movement,” Talley said. “It’s showing up in areas we expect it to show up, and that’s mainly due to the sterile insects being released.”
The sterile insect technique works by releasing sterilized flies into affected areas. When sterile male flies mate with wild females, the eggs do not hatch, helping reduce the wild population.
A retrofitted sterile fly production facility in Mexico is already complete and operating, Talley said. The existing facility was modified specifically for New World screwworm production and is likely producing flies now, with shipments expected to begin around mid-August.
“With the new production facilities coming online, we’re getting higher and higher confidence that it’s a lower likelihood of occurring,” Talley said.
USDA scientists are also developing NovoFly, a strain designed to produce only male flies. Current production creates both males and females, although all flies are sterilized before release.
“When we can only produce sterile males, that increases our production numbers as well as the efficiency of those plants,” Talley said.
NovoFly is not yet available for use in the United States. Talley said the strain must undergo field testing before scientists work with the Environmental Protection Agency to gain approval for its release.
Oklahoma producers also have access to more treatment and prevention tools than were available during the screwworm eradication campaign of the 1950s and 1960s.
“The most important thing for those products to be used for screwworms is that you need to have a veterinarian-client-patient relationship,” Talley said.
Preventative products may provide protection for approximately 14 to 21 days, while treatment products are intended to address an active infestation.
Weather could also affect the pest’s movement. Talley said warm and wet conditions favor fly development, while colder and drier weather can slow population growth.
“Hot, wet conditions allow this fly to be very prolific, whereas cold, dry conditions really suppress its population growth,” Talley said.
No wild New World screwworm flies have been detected between Texas and Oklahoma, Talley said. Surveillance traps in Texas have primarily captured sterile flies released through the control program.
“To my knowledge, to date, they have not trapped an actual wild fly through their trapping program,” Talley said.
Talley said the fly’s natural movement is generally limited, with infestation zones typically extending between 5 and 12 miles. However, the movement of infested animals could carry the pest farther.
“The timely monitoring of animals and looking at animals moving out of an infestation zone is one of the biggest reasons why we’re not seeing a lot of this movement,” Talley said.
While the threat remains, Talley said sterile fly releases, increased production capacity and close livestock monitoring are helping reduce the risk to Oklahoma.
