The horn fly: methoprene in drinking water of cattle for control.

Abstract

Devices were constructed to meter 0.34 mg of methoprene/liter of water automatically into the troughs of drinking water of a 350-animal herd of cattle. The effect on the population of Haematobia irritans (L.), as determined by bioassay of fresh manure collected at intervals from the pasture, was complete inhibition of development of adult horn flies. As a result, the number of horn fly eggs on manure droppings in the pasture declined from an avg 75 to 13 eggs/dropping, and the number of flies was reduced from an average 360 to 7/animal. The untreated group, 12 animals, maintained an avg 300 flies/animal during the initial 5 wk of the 6-wk test. However, all water in the pasture was not treated, and marked sterile flies released on another herd 16 mi distant were found on test animals. Thus, reinfestation was occurring, both from within and outside the test area throughout the test period.