Proper timing of treatment is important when using systemic grubicide pour-ons, spot-ons, or sprays on beef and non-lactating dairy cattle. Summer-time treatments for cattle grubs usually provide two to three weeks of horn fly control. For most effective results, cattle should be treated as soon as possible after heel fly activity ceases, but at least six weeks before grubs appear in the back, i.e. from July to the first killing frost (October). In Ohio it may be best to treat after September 1 to avoid the risk of reinfestation. Do not treat after November 1 for cattle grubs. Do not treat on extremely hot days.
Host-parasite reactions such as bloat, salivation, staggering and paralysis may sometimes occur when cattle are treated, especially in November and December when the common cattle grub, Hypoderma lineatum, is in the gullet, or when the northern cattle grub, H. bovis, is in the area of the spinal cord. Cattle should be treated either before or after these stages of grub development to prevent toxic reaction complications.