Use of Parasitoids and Passive Traps as Alternative Methods of Fly Control on Dairy Farms in Arkansas

Use of Parasitoids and Passive Traps as Alternative Methods of Fly Control on Dairy Farms in Arkansas

Summary

The project was to investigate the use of parasitoids and passive traps as alternative methods of fly control on dairy farms in Arkansas with the objective of lowering chemical resistance of flies and decreasing the likelihood of milk contamination with insecticides. Eleven dairies in Washington County, AR, participated in the project which was conducted for 20 weeks throughout the summer, 2003. Six dairies received weekly shipments of parasites while five dairies served as controls. An agricultural technician distributed the parasitoids and counted horn flies, stable flies and face flies on the cows. To monitor house flies, 3” by 5” index cards were replaced weekly and fly specks were counted to compare fly populations. Fly strips also were used on two dairies that received wasps and on two control dairies to capture flies. This provided a comparison on the number and different types of flies at the facilities. One dairy used a walk-through fly trap for horn fly control; one was also on a dairy in central Arkansas and one on a beef farm. This year we will have three fly traps on dairies in Washington County. Two 4-H families also participated in the trial; one livestock project received parasites and the other served as a control. When compared to control dairies, dairies receiving parasites had only half the number of house flies on fly strips which were allowed to hang for 1 week at the farms. Compared to the 4-H project barn serving as a control, the 4-H project barn receiving parasites had markedly fewer fly specks on index cards all summer long. Although these results are favorable for the use of parasitoids, more work, specifically measuring the degree of parasitism, is needed before we routinely recommend their use on dairy farms.

Objectives/Performance Targets

Our goal was to develop a fly control program for dairy farms by 1) incorporating additional integrated pest management (IPM) practices on the dairies, 2) expanding our past trials to the northwest corner of the state to expose more producers to IPM and parasitoids, and 3) adding walk-through fly traps to the methods of horn fly control. The passive fly trapping method has been shown to provide about 70% control of horn flies. We also put additional emphasis on proper manure management as the project with ADCA indicated that fly populations were related to the amount of manure on the farms. With passive fly traps, producers had (1) a method of non-chemical control for horn flies which should not aggravate resistance to insecticides and (2) greater confidence in IPM strategies to control horn flies without the benefit of excessive insecticide use. Horn flies, face flies, stable flies and house flies are significant fly pests of dairies, both cattle and premises. Research has shown that heavy infestations of stable flies can reduce milk production by 15-30% and horn flies can reduce milk by 10-20%. Fly populations also can develop resistance to chemicals available to control flies and the resistance of flies to insecticides has become a significant problem on dairies in Arkansas.

Accomplishments/Milestones

Parasitoids will be released weekly on the six dairy farms utilizing parasitoids, plus a fly trap was constructed on one of the six parasitoid dairy farms. Monitoring techniques included spot cards in the milking center area to identify numbers of house flies plus fly counts on the cows to verify the effectiveness of parasitoids treatment on a weekly basis. The five control farms were also monitored in a similar manner. A part-time technician was hired to conduct weekly farm visits to cooperating herds using the parasitoids, parasitoids with traps, and traditional fly control methods of insecticides. The technician monitored fly populations in the milking center and fly populations on cows. The parasitoids (Muscidifurax raptorellus, Muscidifurax zaraptor, and Spalangia cameroni) were distributed based on 200/cow/week (or 1000/calf/week if applicable) and were purchased from Beneficial Insectary Company, Redding, CA. The passive fly traps on one of the six parasitoid dairies was a wood structure that cows walked through as they went to the milking parlor. Flies were brushed off the sides and backs of cows by canvas strips and attracted by natural light to a passive screened trapping element where they were captured. House flies were monitored by sticky traps in the holding pen plus spot cards placed in the holding pen, milking parlor, milk house, and dry stack of each farm included in the project. Horn flies were monitored by conducting fly counts on the shoulders, backs, and sides of at least ten milk cows per week on each farm. Stable flies were monitored by counting flies on all four legs of at least ten dairy cows on each farm. Face flies were monitored by counting flies on faces of at least ten milk cows on each farm. The part-time technician provided weekly feedback to dairy producers concerning levels of fly infestation so that the producers knew when they should treat with insecticides. Tentative estimates indicate that producers utilizing parasitoids spent more per cow on fly control costs than producers serving as a control but also had enhanced fly control. Dairies receiving parasitoids had only half the number of house flies on fly strips compared to control dairies. Compared to the 4-H project barn serving as a control, the 4-H project barn receiving parasites had markedly fewer fly specks on index cards all summer long.

Impacts and Contributions/Outcomes

Dairy producers in Washington County now are more knowledgeable of parasitoids and are more interested in the possibility of non-chemical fly control. They still need to have enough confidence in the parasitoids to treat only when fly populations reach a specified level so as to lower overall costs of fly control, the basic principle of IPM. The parasitoids appeared to yield lower numbers of house flies and the possibility of lowering stable fly numbers. One dairy in Washington County used a walk-through passive fly trap for horn fly control last year; one was also on a dairy in central Arkansas and one on a beef farm. This year we will have three on dairies in Washington County with fly traps, with the goal of having less treatment of cows with insecticides, thus reducing the chances of milk contamination and insecticide resistance.