Biological Fly Control on Arkansas Dairies Utilizing Parasitoids
Fly populations can develop resistance to the chemical controls available to dairy producers. Furthermore, chemical controls are generally broad spectrum and can destroy natural fly parasites such as mites, beetles and parasitic wasps. This leaves the producers on a pesticide treadmill with an ever-increasing problem with flies.
Fly populations on cows during the warmer months of the year add to heat stress, since a cow exerts energy to remove flies from her body. This energy expenditure lowers milk production. Fighting flies also takes away from the time cows can spend consuming nutrients (feed and forages). Research has shown that in cases of heavy infestation, stable flies can reduce milk production from fifteen to thirty percent and horn flies from ten to twenty percent.
Our goal is to develop a fly control program on at least six cooperating dairy farms that reduces the use of traditional chemical control by utilizing control with parasitoids (Muscidifurax raptorellus, Muscidifurax zaraptor and Spalangia cameroni). Three additional participating dairy farms will serve as control herds. The reduction in the use of chemical control allows both natural and introduced parasitoids the opportunity to have an environment in which they thrive and increase in population. Parasitoids will be released weekly for fly control. Monitoring techniques such as spot cards and fly counts on cows will be utilized to verify the effectiveness of the parasitoids on a weekly basis. This program has potential to not only provide an economic improvement (prevent milk production from being reduced due to fly populations) but also reduce the amount of chemical applied which will create an improved environment for natural fly parasites.
Horn fly monitoring will be conducted by counting flies on the shoulders, backs and sides of the milk cows on each farm. Stable fly counts will be conducted by counting flies on all four legs of the dairy cows on each farm. Spot cards will be placed in the holding pen and the milking parlor of each farm to monitor the population of house flies. Fly populations on the cooperating farms will be compared to fly populations on the control farms to demonstrate the effectiveness of the parasitoids. Economics of the various fly control methods will be compared to demonstrate the cost effectiveness of the parasitoids.