The horn fly, Haematobia irritans, is a permanent, blood-sucking parasite of livestock which, under dense populations may be responsible for reduction in either weight gains or in milk production. Spraying is the most common method of horn fly control but involves capital investment in power-spray equipment, excessive labor for repetitive spray treatments, and in some instances, considerable animal stress. An earlier study showed the effectiveness of Ronnel when this animal systemic insecticide was mixed with cottonseed supplement and fed throughout the summer season. Cattle grub control also was obtained the following winter, but high costs (three cents per head per day) and the methods of supplementing summer rations were not applicable to all winter livestock management operations. For these reasons, and because of the threat of a face fly invasion of California, the use of insecticidal dust-charged burlap sacks (“dust bags”) was investigated in 1966 and successfully field tested during the next two years.

Photos are by L. L. Dunning.