Treat adjacent fencerows or grassy areas along with the portions of the orchard in which trouble usually occurs. During heavy, persistent snow cover, a few voles can cause serious damage. Thus, it may be necessary to rebait in midwinter. Place bait in snow tunnels, air holes, and near fresh bark damage. To achieve proper vole control with zinc phosphide bait, wait until the weather is likely to be fair and dry for at least 3 days.
Zinc phosphide breaks down and washes off in damp weather.
Orchard baiting followed by rain is generally ineffective. Exclusion Many types and brands of tree guards are available commercially. The tight spring like plastic wraps are not recommended as they can girdle trunks in later years, delay hardening off of the trunk tissue and provide a safe haven for borers. Mesh type guards rather than solid plastic are also preferred so that pesticide sprays can reach the trunk. At the very least the guards should be anchored at the base with some soil or round pea gravel.