Report aids ranchers in warding off pesky parasite as warming helps it thrive

Jan. 23, 2023, 11 a.m. ·

horn flies.webp
Marcia O'Connor / Flickr Creative Commons

A recently published report by the University of Wyoming Extension looks into methods to mitigate the impacts of horn flies on the cattle industry throughout the Cowboy State and Mountain West.

Horn flies – an invasive species first discovered in the U.S. in the late 19th century – are among the most damaging parasites ranchers and producers have to deal with, and they may be becoming more prevalent in the region due to climate change.

Derek Scasta, a UW professor and rangeland extension specialist who co-authored the report, said horn flies feed on the backs of cows. The animals try all kinds of things to keep the pests away.

“Things like swinging their head, stomping their feet, [and] swishing their tails,” he said. “Shaking their hide.”

That behavior leads to lower performance among cattle. The animals gain less weight and produce less milk. Scasta said some ranchers have also observed reduced grazing times or nursing. Nationwide, the beef cattle industry loses $2.19 billion every year due to horn flies, according to the report.

“They've spread all over the country,” Scasta said. “They're up into Canada, and they're certainly all over cattle here in Wyoming.”

In previous decades, Scasta said horn flies tended to stay away from cooler, high-elevation climates. They’re still more common in lower areas – particularly in more southern states like Texas – but as the climate changes in the region, ranchers may begin to be affected by horn flies more often and for longer periods of the year.

“If we continue to see warming, it may become more of an issue that we may need to pay more attention to,” Scasta said. “As the climate warms, the environment becomes more and more suitable.”

Scasta and a team of researchers looked into several methods for how to reduce the negative impacts of horn flies, including spraying entire herds with bug repellents, attaching ear tags filled with insecticide and rotating or moving animals more often on the landscape. Scasta hopes cattle producers use his guide to find the most economical solution for their particular situation.

“One of the problems that happens with flies on livestock is, by the time we think it's a problem, it's probably been a problem for a while,” he said. “We tend to be a little bit reactive instead of proactive.”

Scasta also said he’s constantly talking with other ranchers in the region to see what control methods may be emerging. One possibility is selecting animals for greater parasitic tolerance and breeding them. Another is purposely placing other, less damaging insects in the area that could eat or ward off parasites. Even feeding garlic to cows has been shown in some research to reduce horn fly impacts.

Scasta said the most important part of his report is to raise awareness of the issue and to highlight potential solutions for cattle producers. During the colder winter season when the pests are dormant, it can be the perfect time to come up with a game plan for the busier summer season.

This story was originally produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, the O'Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting