Long Term Vole Control in Ontario Apple Orchards

'!he results obtained so far in this 3 year study have shown that the plots with poisoned bait feeder stations suffered significantly less tree girdling than the plots treated with the fall broadcast application of 2% zinc phosphide. Similar timings were also observed in number of voles per plot, however, the vole population was much lower than the previous year. Cbnsiderable interest has been shown by apple growers in adopting this method of vole control at a commercial level. Introduction, Methods ar:rl Materials: '!he importance of vole damage ar:rl a lack of significant research on vole control in Ontario were described in the proceedings of the Sixth Eastern Pine ar:rl M=adow Vole Symposium (Siddiqi ar:rl Blaine, 1982). '!he methcds ar:rl materials used were also mentioned in this publication. Dlring the course of this study, so far the following observations have been made at all the four locations. 1. Estimat.ion of the meadow vole population by mark ar:rl release method: in the fall 1981 before installing the bait stations; in the spring ar:rl the fall of 1982. 2. Estimating number of the meadow voles per site by exhaustive snap trapping 30 days after bait station ar:rl broadcast application. 3. Percentage of trees girdles by the meadow voles was recorded in the spring 1982. Extent of girdling was not measured. After initial installation of the bait stations in the fall of 1981, the stations were cleaned ar:rl ref illed in the spring 1982 am again in the fall 1982. '!he formulation of brodifacoum (0.005%) was replaced by a newer formulation containing 0.001% of the toxicant (Volid, from leI Jlrnericas Inc). Results am Discussion: Number of meadow voles per plot, as estimated by the Schnabel imex, for fall 1981, ar:rl soring ar:rl fall 1982 are presented in Table 1 for Orono, in Table 2 for Nbrval, am in Table 3 for Milton locations. Nb meadow voles were captured at Belwood, the fourth location. It is obvious from these tables that the vole population declined greatly from fall 1981 to fall 1982. '!he number of voles per plot were significantly more in the zinc phosphide broadcast treatment as compared to the other rodenticides in the bait stations at Orono in fall, 1982 (Table 1). Nb similar differences were observed at any other locations (Table 2 am 3).