Penn State University researchers urge growers to place bait for voles in late fall to reduce populations before winter. Timing of the control measures influence the success of the program. Bait should be placed when the weather is fair and dry for at least three days. Wet weather reduces the effectiveness of toxicants. Baits are most effective when naturally occurring foods are limited.
Voles are active day and night, year-round. The peak vole activity occurs at dawn and dusk. Voles do not hibernate.
A meadow vole presence can be identified with the presence of surface runways in the grass. Pine voles do not use surface runways. In apple orchards, tiny, elongated tooth marks on apples on the ground are an indication of a vole presence.
In order to determine the quantity of voles in the orchard, Penn State researchers suggest using the apple indexing method. Place a slice from the cheek of an apple into a meadow vole runway or pine vole tunnel. Check the apple after 24 hours for vole tooth marks, and this will indicate where vole activity is at its highest. One pine vole consumes 0.5 ounces of an apple in a 24-hour period and one meadow vole consumes about 0.6 ounces.
The apple indexing method helps orchardists to assess whether the population is increasing or decreasing or whether a treatment has an impact on population size.
For more on vole biology and a fall control program, click here.
Source: Penn State University Extension bulletin