The effectiveness of five rodenticides and three application procedures in controlling Microtine voles ( Microtus montanus) in Washington State apple orchards

Abstract

Four formulations of the acute toxicant zinc phosphide and one formulation of the subacute toxicant chlorophacinone were evaluated on voles ( Microtus montanus) in two Red and Golden Delicious apple orchards in north central Washington during the spring. Three treatment techniques combining cultural practices with differing methods of bait application were compared concurrently. Raking, followed by a single broadcast application of baits or the hand-placement of baits, was the most effective treatment. A second bait application gave a slight improvement only when no cultural work was done, and then only with two of the five baits tested. Whole wheat and steam-rolled oat baits with 2% zinc phosphide and Rozol® chlorophacinone baits were usually more effective than zinc phosphide on cracked corn or ZP Rodent Bait AG®.