Scientists found that a single application of granular cyromazine sprinkled on a hay-feeding site reduced the number of adult stable flies emerging by 97 percent. Treatments took about 10 minutes, cost $10 per site, and remained effective for 10 to 20 weeks.

“It’s something producers can put in a pickup truck and don’t have to mix or spray,” Taylor says. “They can quickly treat sites while doing other chores or checking on cattle.”

A ‘push and pull’ strategy

Identifying the attractants or substances that lure females to a particular site to lay their eggs may help scientists find ways to reduce their populations.

“When gravid females — flies with eggs — reach an egg-laying site, we believe they use the olfactory sensors on their antennae to gather information related to nutrition,” says AMRU entomologist Jerry Zhu. “They then make a decision as to whether it is the right area to lay their eggs.”

Zhu is using what he calls a ‘push and pull’ strategy to control stable flies. The ‘push’ involves driving stable flies or other filth flies, like house flies and horn flies, away from livestock with a repellent. Plant-based chemicals that are low in toxicity, such as those found in catnip, are being used as experimental treatments.

“Catnip oil and its active compounds — nepetalactones — are powerful repellents against stable flies,” Zhu says. “Catnip is probably the best repellent identified, so far, for flies that bite. Catnip oil is also a good larvicide,” meaning it can be used for reducing stable fly larval development, he adds.

Zhu and his colleagues developed several sprayable catnip oil formulations for reducing stable fly field populations. Through a cooperative research and development agreement, Zhu partnered with Microtek Laboratories, Inc., to test a novel granular catnip product that can deter egg-laying.

The ‘pull’ part of Zhu’s strategy involves developing attractants to lure stable flies into a trapping system that can be combined with a low-toxicity insecticide or a sticky substance.

Zhu and Taylor are also working with AMRU entomologist Kristina Friesen, who is studying microbial communities associated with stable fly larval development sites.

“In my mind, the long-term solution to stable fly control is a cultural solution,” Taylor says. “Even though we’re developing strategies such as chemical control, our long-term objective is to provide producers with methods to raise cattle without providing larval developmental sites for flies. That’s the real goal.”

This research is part of Veterinary, Medical, and Urban Entomology, an ARS national program (#104) described at www.nps.ars.usda.gov.

"Going Beyond the Barnyard To Stop Stable Flies"was published in the January 2013 issue of Agricultural Research magazine.