Influence of Groundcover on the 

 Incidence of Vole Activity and Damage 

 in Apple Orchards 



James A. Parkhurst 



Department of Forestry & Wildlife Management, 



University of Massachusetts 



In the course of normal feeding activities, 

 both meadow voles (Microtus pennsylvanicus) 

 and pine voles (M. pinetorum) are capable of 

 inflicting substantial physical injury on apple 

 trees by girdling the lower trunk or stripping the 

 protective covering from lateral roots. Even 

 where inj ury to trees is not immediately evident, 

 a reduction in fruit yield or tree vigor may 

 indicate the presence of vole activity. Because 

 any loss of production represents a potential 

 economic impact, orchardists have been search- 

 ing for practical methods to control or prevent 

 vole damage. In many cases, the method of 

 choice has been the application of rodenticides in 

 an attempt to reduce the size of the vole popula- 

 tion. However, with increasing costs for materi- 

 als and labor plus added pressure from a "more 

 aware" general public demanding use of only 

 environmentally sensitive techniques, applica- 

 tion of broadcast rodenticides has come under 

 scrutiny. The use of cultural control techniques 

 is receiving renewed interest and some on-going 

 investigations are beginning to produce some 

 fascinating results. A paper recently prepared 

 by researchers at Cornell University (Curtis, P. 

 D. and I. Merwin. 1990. Meadow vole activity 

 and damage to apple trees in relation to orchard 

 ground cover management. Proc. 52 nd Annual 

 New York State Pest Management Conference, 

 Cornell University, Ithaca, NY. 9 pp.) examines 

 the influence of different groundcovers and 

 mulches on vole activity and feeding damage to 

 apple trees. This article summarizes some of the 

 findings of their research. 



Methods 



When the Cornell experimental orchard ini- 

 tially was established in 1985, Empire and 

 Jonagold trees on MM.lll rootstocks were 

 spaced three yards apart and a groundcover of 

 70% Elka ryegrass (a dwarf perennial), 30% 

 Ensylva red fescue, and a starter crop of oats 

 was planted beneath the trees. In this study, 

 researchers examined vole activity and damage 

 on 2.5-yard-wide plots established within the 

 dripline of trees and using eight experimental 

 groundcovers (treatments), including: 



(1) existing sod groundcover, treated with 

 glyposate 2.5 yards wide; 



(2) same as above, but only 1.5 yards wide; 



(3) live crownvetch; 



(4) bare or nearly bare ground following 

 multiple herbicide treatments; 



(5) sod mixture of red fescue and perennial 

 ryegrass mowed to consistent height of 2 

 to 5 inches; 



(6) sod mixture (as in #5), but unmowed 

 and treated with growth suppressant 

 and selective herbicides; 



(7) hay/straw mulch 6 inches thick, renewed 

 annually; and 



(8) clean soil maintained by monthly roto- 

 tilling to a depth of 4 inches. 



Metal mouse guards (12 inches high) were 

 placed 2 inches deep on all trees and normal 

 winter applications of zinc phosphide (bait and 

 broadcast) were continued on all plots from 1986 



Fruit Notes, Summer, 1991 



