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- Author or Editor: Thomas P. Sullivan x
Abstract
Removal of all vegetation with herbicides over the total orchard floor or only in tree rows significantly reduced montane vole (Microtus montanus Peale), meadow vole (M. pennsylvanicus Ord), and northern pocket gopher (Thomomys talpoides Richardson) populations and damage. Herbicide treatments in four test orchards were carried out during May, July, and Sept. 1983 to 1985. Average overwinter abundance of voles was reduced 53% to 99% on treatment areas. Several vole populations went to extinction in the third year of herbicide treatment. Incidence of tree damage was 40.6% and 9.6% with feeding intensities of 17.2 cm2 and 0.4 cm2 of bark and tissues removed per tree on control and treatment blocks, respectively, during a peak year in abundance of voles. Pocket gopher populations and damage were significantly lower in treatment than control blocks. Deer mouse (Peromyscus maniculatus Wagner) and yellow pine chipmunk (Eutamias amoenus J.A. Allen) populations generally increased on treated areas. Use of herbicides to control orchard floor vegetation is an effective means of rodent damage control.
Living mulch cover crops can improve soil health and build organic matter, yet their use in fruit orchards comes with a risk of encouraging meadow vole (Microtus pennsylvanicus), a rodent that can be destructive to fruit trees. Several living mulch cover crop species were assessed in an apple (Malus ×domestica) orchard understory along with wood chip mulch and bare ground. Desired species characteristics were weed competitiveness, low growth habit, nitrogen fixation, and potential rodent repellency. Legume species included birdsfoot trefoil (Lotus corniculatus), medic (Medicago spp.), and subterranean clover (Trifolium subterraneum), which were planted in solid stands as well as mixtures. Nonlegume species included sweet woodruff (Galium odoratum), sweet alyssum (Lobularia maritima), creeping thyme (Thymus serpyllum), and colonial bentgrass (Agrostis tenuis). Meadow vole presence was evaluated in fall and spring with point-intersect and run-length measurements. A legume mix (medic, birdsfoot trefoil, subterranean clover, and colonial bentgrass) had the highest meadow vole presence, with no reduction under the “sandwich” system of tilling either side of the tree trunks while leaving a cover crop in a narrow strip with the trunks. The nonlegume mix [colonial bentgrass, sweet alyssum, creeping thyme, and fivespot (Neomophila maculata)] had similar results. However, the sweet woodruff (planted in the “sandwich” system) had significantly lower presence of meadow voles than the other living mulches. Wood chip mulch, cultivation, and bare ground control were all similar, with very low presence, indicating low risk of meadow vole damage. The results from the sweet woodruff suggest that we need more research on the potential to select living mulches that are nonattractive or repellent to meadow voles for use in orchards.