Orchard groundcover management systems affect meadow vole populations and damage to apple trees

Meadow vole (Microtus pennsylvanicus Ord) populations, feeding activity and damage to young apple (Malus xdomestica Borkh,) trees were monitored for s everal years in a New York orchard by direct observation, trap counts, and a feeding activity index in various groundcover management systems (GMSs), Meadow vole population density differed among GMSs, with consistently highe r densities and more trees damaged in crown vetch (Coronilla varia L,), hay -straw mulch, and red fescue (Festuca rubra L.) turfgrass tree-row strips. Vole densities were high in autumn and low in spring each year. Anticoagula nt rodenticides and natural predation did not adequately control voles in G MSs providing favorable habitat. Groundcover biomass per m(2) was weakly co rrelated with vole densities in 2 of 3 years, while the percentage of soil surface covered by vegetation was not significantly correlated with vole po pulations. Applications of thiram fungicide in white latex paint were bette r than no protection, but less effective than 40-cm-high plastic-mesh guard s for preventing vole damage to tree trunks. A combination of late-autumn t rapping, close and consistent mowing of the orchard floor, trunk protection with mesh guards, contiguous habitat for vole predators, and herbicide app lications within the tree rows provided effective control of meadow-vote da mage to trees at this orchard during 3 years without applications of rodent icide baits. Chemical names used: Tetramethylthiuram disulfide(thiram).