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The efficacy of using 0.01% chlorophacinone on steam-rolled oat (SRO) groats applied in CA alfalfa by spot-baiting/hand baiting around burrow entrances (~11.5 g) to control free-ranging Belding's ground squirrels (Spermophilus beldingi) were compared in 6 randomly assigned square treatment units (TUs). Four TUs were given the rodenticide and 2 treated with placebo bait. Each TU was a 0.4 ha square surrounded by a similarly treated 5.5 ha square buffer zone. Baits were applied on May 13 and re-applied, on May 20 and May 22, after 7 days of un-forecasted cool wet weather greatly reduced their above ground activity. Pesticide (EPA SLN CA-890024) efficacy was calculated as % reduction (PR) of ground squirrels on each TUs measured directly by visual counts (VCs) and indirectly by active burrow counts (ABCs). VCs and ABCs provided mean PRs that met US EPA's 70% minimum standard efficacy threshold for field rodenticides (x = 73.5%, SD ± 13.3; x = 80%, SD ± 6.2, respectively). ANOVA results of the PRs were highly significant (F = 29.72, df 1/4, p = 0.0055 and F = 72.92, df 1/4, P = 0.001, respectively). All carcasses (38) located above ground were analyzed for pesticide and 80% had detectable levels in whole animals (x = 0.1131 ppm, SD ± 0.0928). Suggestions to improve the pesticide's efficacy and lessen its potential non-target hazards were discussed.

We conducted a study in 2 heavily infested orchards in the mid-Hudson Valley of New York to evaluate methods for detecting the presence of meadow voles (MV, Microtus pennsylvanicus) and pine voles (PV, M. pinetorum) under apple trees. We quantified several possible signs indicating the presence of voles in each of the 4 quadrants under the canopy of each tree, and then set and monitored traps until capture success in the orchard declined to zero. There was no evidence that the 4 quadrants differed with respect to any of the variables examined. The apple slice index (ASI) was the best indicator for both species. Detection improved significantly (P < 0.05) when the ASI was used in conjunction with the number of runways (MV) or tunnels (PV) under the tree, although neither of the latter 2 signs was by itself a reliable indicator. The ASI and search for runways and tunnels should be conducted in at least 2 quadrants under each tree. The significance of these findings for managing voles in apple orchards is discussed.