U.S. Department of Agriculture researchers are developing strategies to help livestock producers control stable flies, the most damaging arthropod pests of cattle in the U.S.
An economic impact assessment by scientists at the Agricultural Research Service (ARS) Agroecosystem Management Research Unit (AMRU) in Lincoln, Neb., looked at four sectors of cattle production: dairy, cow/calf, pastured and range stocker and animals on feed. They found that stable flies cost the U.S. cattle industry more than $2.4 billion each year due to reduced milk production in dairy cows, decreased weight gain in beef cattle and lower feed efficiency.
Stable flies are a problem not only in barnyards and stables for which they are named, but in pastures as well, ARS said.
AMRU entomologist David Taylor and his colleagues found that this is partly due to placing large bales of hay in fields as supplemental feed for cattle during winter. Wasted hay, manure and urine accumulate in these feeding sites and create an ideal habit for stable flies.
To find an easy, inexpensive, quick way to control stable flies, Taylor tested cyromazine, an insect growth regulator that interferes with molting and proper development of an insect's external skeleton, ARS said. A single application of cyromazine sprinkled on a hay feeding site reduced the number of emerging adult stable flies by 97%. The treatment took 10 minutes, cost $10 per site and was effective for 10-20 weeks, ARS reported.
Other potential methods for controlling stable flies include what AMRU entomologist Jerry Zhu calls a "push and pull" strategy. The "push" requires using a repellent to drive flies away from livestock, ARS noted, adding that treatments contained effective plant-based repellent chemicals like catnip that are low in toxicity. The "pull" involves developing natural attractants or substances associated with the flies' environment to lure and trap them.
So far, Zhu and his team have developed several catnip oil formulations to reduce stable fly field populations. In collaboration with Microtek Laboratories Inc. of Dayton, Ohio, the researchers are testing a new granular catnip product that prevents stable flies from laying eggs.