ECONOMICS AND CONTROL OF DAMAGE CAUSED BY LOW-DENSITY POPULATIONS OF MEADOW VOLES IN ONTARIO APPLE ORCHARDS

Live trapping and questionnaires were used to evaluate amount, distribution, and costs of control of damage to Ontario apple trees by meadow voles (Microtus enns lvanicus) in 1981-82. In a sample of 180 orchards, 5802 (0.77%) trees were damaged or killed by voles. Orchards with high levels of damage (\u3e 2.5%) were smaller than the average orchard in our sample. Application of rodenticides showed no relationship to levels of damage, but was effective in short-term population reduction. Growers spent an average of $17/ha on rodenticides and $38/ha on herbicides, and they estimated that voles destroyed 2% of their crop each year. About 55% of our sample of growers stated that damage by voles was more significant than that caused by insects or other pests. In the 1981-82 season, vole numbers were lower than in 1980-81, and reported levels of damage were also lower. These differences are discussed