Fall is the best time to treat, since grubs are killed before they cause major damage. Cattle can be treated with systemic insecticides from mid-September to December 1 in Alberta. Cattle should not be treated in December, January, or February because side reactions caused by the death of the grubs can occur. Spring Insecticide Treatment Spring treatment is a clean-up treatment and should not be considered as the producer's primary control program. May. With spring application of systemics, between 95 and 100 per cent of the grubs will be controlled if infested cattle are treated between March 1 and April 15, with reduced control thereafter.
Rotenone provides good spring grub control if it is applied properly.
Treatment methods Each kind of warble control insecticide is applied differently. The following notes related to the various application methods may assist in obtaining good grub control. The animal must be wet to the skin. Better application is required when animals have thick long winter hair. A spray that is too coarse will splash off the animal and be wasted.