During this period they damage the meat and hide of infested animals and are responsible for reduced milk production in lactating cattle and lower weight gains in calves. Both cattlemen and packers incur severe economic losses in the absence of a warble management program. In Alberta, there is a province-wide organized warble control program helping Alberta cattlemen and the packing industry. According to the Agricultural Pest Act, all Alberta producers must take active measures to control warbles in their cattle. To manage warbles at the farm level, it is necessary to understand the biology of the insect and the method of action of the various pest control products.
Warble flies develop from the grubs that drop from cattle in the spring.
The flies, which are rarely seen, resemble small bumble bees. The flies are active on sunny days. They do not bite or sting, but their egg laying activity causes cattle to panic. Warble flies will chase cattle into water or shade. The female adult of the common cattle grub lays groups of eggs on the lower portions of cattle from May to June.