If sprays are used, check the animals at about 14-day intervals to determine if the population is under control. Most insecticides will not control the eggs, and two treatments may be necessary to eliminate the infestation. In addition to sprays, dust bags can be used for lice control. Note the treatment interval before freshening. Cattle Grubs Cattle grubs are immature heel flies.
Heel flies deposit eggs on the hair of cattle early in the spring.
As the grubs hatch, they migrate down the hair strand to the follicle and bore into the animal. The next 7 to 8 months are spent as internal parasites. The grubs migrate through the tissue to the loin area where they encyst, cut a breathing hole in the skin of the animal on the back-line and complete their larval development. When mature, they emerge through the breathing hole, fall to the ground and pupate. In the spring, the adult heel flies emerge and start the life cycle again by depositing eggs on cattle.