Ohio State University Extension Bulletin

Livestock and Livestock Building Pest Management

Bulletin 473

When to Treat for Cattle Lice

Systemic organophosphate pour-ons & spot-ons and ivermectrin pour-on & injection for lice control on beef and non-lactating dairy cattle are convenient because Ohio winters are often very cold, preventing spraying or dipping. Grub treatment before Ohio's November 1 cutoff date will often not take care of cattle lice problems. Louse eggs are not susceptible to insecticides and therefore animals should be reexamined about three weeks after treatment to determine if viable lice eggs have hatched and reinfected the herd.

Do not use grubicides such as coumaphos (Co-Ral), famphur (Warbex), fenthion (Tiguvon), fenthion (Spotton), phosmet (Prolate, GX-118) or trichlorfon (Neguvon) during November and December on Ohio cattle not previously treated for grubs due to possible host-parasite reaction. After January 1, grub larvae have migrated from the spinal canal, or esophagus, and usually encyst in the back and cattle may then be safely treated with grubicides. It is then safer to treat for lice to minimize the host-parasite reaction.

For cattle previously treated for grubs, a second treatment later in the season may become necessary should lice become a problem. The second treatment usually should not be applied sooner than 35 days after the first treatment. Be sure to follow instructions on the label for any safety precautions.

There are spot-ons and pour-ons such as cyfluthrin (Cylence), fenthion (Lysoff, Lice-Chek), ivermectin (Ivomec), lambdacyhalothrin (Saber), and permethrin (Brute, Delice, Expar, Hard-Hitter, Permectrin) registered for lice control and applied any time throughout the autumn and winter months because they do not kill grubs. However, fenthion has a warning of rare (but possible) host parasite reactions. Be sure to follow instructions on the label for any safety precautions.

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