MANAGEMENT OF PINE VOLES

The pine vole (Microtus pinetorum) damages apple trees in western North Carolina, sometimes spectacularly. The current research monitors populations in orchards for several years to compare damage in different management practices. Recommendations for orchard management to reduce damage are devised and used to i l l u s t r a t e the process of a p p l i c a t i o n of basic knowledge. Populations of voles were monitored by 3 s i m p l e methods. Data on reproduction were obtained. Data on home range and mortality were found in the literature. In two counties, the orchards generally had grass in the a l l e y s and sometimes a growth of weeds under the tree canopy. In two other counties (less h i l l y ) the orchards were much cleaner. Numbers of voles and amount of damage were much higher in the less clean orchards. A management program should i n c l u d e mowing 5 times a year, c l e a r i n g vegetation from under the tree, removing prunings, restricting d i s t r i b u t i o n of fertilizer and, after harvesting, inspecting and cleaning especially vulnerable parts of the orchard. The p i n e vole (Microtus pinetorum) has damaged apple trees for decades along the Appalachians from northern Georgia to Massachusetts. The voles tunnel at the base of the trees and gnaw the trunk underground, often k i l l i n g the tree. The damage may be spectacular. The grower in e a r l y summer, e s p e c i a l l y in a dry s p e l l , may be surprised to see the leaves on a tree suddenly turn y e l lo w and drop in a few days. Control of voles has r e l i e d on a series of poisons since at least 1933 when the Fish and W i l d l i f e Service i n i t i a t e d a substantial program. The purpose here is to record the results of several years of research designed to develop recommendations for a more l a s t i n g method of reducing damage. Life history data are included as a basis for the recommendations. An additional purpose is to i l l u s t r a t e the process of a p p l i c a t i o n of basic research to the practical problem of reducing damage. The research here reported was planned about 1970 in the following steps: (1) Selection of ecological p r i n c i p l e s that might be helpful (2) C o l l e ct i o n of necessary data (3) Preparation of management p l a n (4) Referral to action agency (Agr icultural Extension Service) for educational program. A l l of these steps involved consideration of other pests of apples and also the harvesting of the fruit. Some comments on p o l i t i c a l r e a l i t i e s w i l l be added. The problem is not to get r i d of p i n e voles as such but to reduce damage to apple trees. Thus, methods that restrict or impede the access to the tree w i l l be useful. The magnitude of damage al s o needs consideration and evaluation, because the costs for control should be kept less than the costs of the damage. But data on damage from voles are d i f f i c u l t to obtain. Losses from other pests such as root rot must be assessed.