Research provides stable fly monitoring and control tools

The Issue

High levels of stable flies on dairies are more than a nuisance. The bites also reduce milk yields. To keep stable flies at bay at dairies, it is standard procedure for dairy operators to hire a pest control service that sprays the premises with pesticides every two weeks during fly season, at an average cost of $250 per treatment. Because of pesticide resistance developing in the insect population, such sprays for stable flies are rarely effective. This management practice wastes dairy resources, adds to the pesticide load in the environment, and leads to increased pesticide resistance.

What Has ANR Done?

UC Cooperative Extension dairy advisor Nyles Peterson and UC Riverside entomologist Brad Mullens have proposed and helped develop easy and accurate methods for predicting, monitoring and safely controlling stable fly populations. The level of late-season rainfall, they found, provides operators an early warning about spring fly population levels. The more late-season rain, the greater the springtime fly population dairies should expect. In high-rainfall years, dairy operators get two-months advance notice about the flies’ expected population levels and can work to limit the flies’ preferred breeding places by keeping corrals clean, disposing of moist decaying feed, and properly maintaining manure. The scientists have also identified two easy methods to monitor fly populations as the season progresses. Dairy operators can count the number of times cows flick their tails in a minute or count the number of flies resting on cows’ legs. Chemical control may be delayed -- without significantly reducing milk production -- until tail flicks reach 10 per minute or until there are on average five flies per leg.

The Payoff

Research saves money and reduces chemical usage

Typically, dairy operators begin costly chemical control of stable flies based on the calendar, the weather or by making an educated guess about fly population levels. However, the UC research has found that dairy sanitation before fly season reduces the amount of flies on dairies and that chemical treatment may be delayed until flies reach easy-to-determine threshold levels. These methods save the dairy money, reduce the amount of pesticides in the environment and help prevent insect pesticide resistance.


Supporting Unit: San Bernardino County

Nyles G Peterson
Dairy Advisor - San Bernardino
777 E Rialto Ave
San Bernardino, CA 92415-0730
(909) 387-3318