NovoFly: A New Tool for Screwworm Control

USDA researchers have developed NovoFly™, an all-male strain of New World screwworm designed to improve the Sterile Insect Technique, or SIT. Screwworm has been controlled with sterile flies for decades, and this method helped eliminate the pest from the United States by 1966. The technique is important again because recent screwworm resurgences threaten livestock and wildlife in New Mexico and Texas.

SIT works by releasing sterilized male flies near places where screwworm is present. These males mate with wild females, but the eggs that result do not develop into larvae. Screwworm larvae feed on animal tissue and often enter wounds or mucus-lined openings. By stopping new larvae from developing, SIT can reduce pest populations and lower the need for insecticides, veterinary care, and medications.

However, conventional SIT has a limitation because sterile female flies may also be released with the males. Sterile females do not provide the same reproductive control as sterile males, which prevent wild females from producing new larvae. NovoFly™ was developed to address this problem by using a genetic switch that kills female larvae during early rearing but does not affect males. This allows researchers to raise more males with the same amount of artificial diet and equipment. Producing only males could essentially double the number available for sterilization and release without major changes to existing facilities, while also giving the sterile males more chances to mate with wild females.

NovoFly™ is currently undergoing regulatory approval by the Environmental Protection Agency. If it is approved, the strain will be used at designated screwworm rearing facilities. USDA's Animal and Plant Health Inspection Service coordinates SIT activities in the United States, Mexico, and Central America. Researchers say the development of NovoFly™ could also support future efforts to control screwworm.

Why could producing only male flies make the Sterile Insect Technique more effective?