Large vole populations in yards and fields can be reduced most effectively with toxic baits. Zinc phosphide is federally registered for controlling voles and is available in formulated pellets or treated grain. It usually is a Restricted Use Pesticide that may be purchased and used by Certified Pesticide Applicators only. Contact your local Extension educator for information on becoming a Certified Pesticide Applicator. Some formulations of zinc phosphide are packaged in small containers and are registered as General Use Pesticides that can be purchased and used by the general public. You may find that the toxicant is most effective when administered in the fall and early spring when voles have few alternative food sources. Pre-baiting with untreated oats or pellets for two to three days may help improve bait acceptance and thereby increase the toxicant’s effectiveness at reducing the vole population. Zinc phosphide is NOT for indoor use.
To reduce the potential for affecting nontarget species, avoid placing pre-bait or toxicant on bare soil or in piles. Use zinc phosphide during a period of fair weather to protect the toxicant from moisture. The use of bait stations will further decrease the risk of nontarget species and moisture from reaching the toxicant. Contact your Extension educator on where to obtain them.
Read all pesticide product labels thoroughly, and comply with all directions given.
Zinc phosphide baits can be applied by hand in spot treatments by placing it in runways or burrow openings. Hand-baiting is the only application method that can be used in urban areas and lawns, ornamental plantings, parks, and golf courses. When placing toxicant in pine vole holes, take care not to damage the hole or surrounding area. Pine voles are very fastidious. Any disturbance may result in the pine vole “sweeping” the toxicant out of the burrow during its cleaning activities.
Before baiting, mow the grass to increase the amount of bait that reaches the trails and burrows used by voles.