Date of this Version
The control of cattle grubs is discussed here, as are possible insecticide reactions, warnings and restrictions.
Cattle grubs are the immature or larval stages of heel or warble flies. Losses from this insect begin with the fly stage in the insect's life history. As flies seek animals on which to deposit eggs, cattle become frightened and run. The running animal has its tail in the air, bent over the back. This behavior is termed "gadding."
Cattle fail to graze normally during the warble fly season because of gadding. They seek shade or stand in water to avoid the flies. The failure to graze normally results in decreased milk production and subnormal weight gains. Further losses occur when cattle, in their efforts to escape the flies, run through fences or into other objects.
Slaughter losses result when grubby areas must be trimmed from the carcass and from the decreased value of hides containing grub holes.