Certain pour-on applications approved for grub and lice control are also effective against horn flies. Direct application treatments should begin in the early spring when fly populations reach 50 to 100 per animal and continued at intervals, based upon resurgent fly populations, throughout the duration of the horn fly season. Cattle spraying by aircraft has been used with some success in South Dakota and Nebraska. When using self-treating devices, the degree of horn fly control is closely associated with the frequency of application. They should be positioned near mineral feeders, over gates leading to watering areas, along alley ways, and in cattle loafing areas.
Regular maintenance is essential to ensure that self-treating devices are working properly.
Feed through insecticides operate by passing through the animals digestive tract to kill fly larvae in the feces. Some feed through insecticides will also kill adult flies attempting to lay eggs on the manure pads from treated cattle. Phenothiazine also aids in control of certain cattle worms. One or both products are available in mineral mixtures, feed blocks, and as premixes. Unfortunately, feed through insecticides often provide less than satisfactory horn fly control since not all animals in the herd consume the product at a uniform rate.