I would like some information about controlling voles in my apple orchard and high tunnel; preferably non-chemical
Thank you for your inquiry. Below is information about voles that I have taken from "Vole Management: "Winterizing" your Orchard from Vole Damage" by R. Crassweller and T. Baugher:
One of the last tasks in getting orchards ready for winter is planning your strategy to control voles and prevent their damage.
The first step in any vole control program is to monitor the orchard to determine the extent of the population present. Monitoring consists of providing some “sheltered” locations in the orchard such as arched roofing shingles, tires cut in half, “PVC T-tubes,” used aluminum soda cans or anything that can provide temporary shelter for the voles. Monitoring stations are best concentrated close to where orchard blocks adjoin woods or open fields but should also be scattered throughout large blocks.
The apple index method is the most common method of monitoring. First place the “shelters” in the orchard, preferably where you may see or suspect vole runs. Make a grid map of the locations of the stations. Leave them in place for 3 to 5 days before baiting them. To bait them cut 0.5 inch square chunks of apples and place them under the shelter. Be sure to map the orchard as to the locations of the bait stations. Wait 24 hours and return to the bait stations and examine the apples for evidence of chewing on the apple or its absence. Marking the grid map you created with a + or – will give you a visual representation of the vole activity. Wherever there is a concentration of the vole population will be the area that you need to concentrate control measures.
Another method of determining the population is to set traps and monitor them. (Note: trapping is not an efficient control method in large orchards). For meadow voles, place the traps in runways, flush with the ground and perpendicular to the runway. Place the trigger end in the runway. For pine voles, locate a tunnel and place the trap within the tunnel and perpendicular to it. Put a cover such as a bent roofing shingle or box over the traps. This helps protect most nontarget animals and makes the voles more likely to enter the site.
Cultural controls can be utilized to reduce populations and potential damage. The first line of defense is to mow the orchard row middles closely to reduce potential cover for the voles. A closely mown sod will expose voles to attacks by predatory birds such as hawks and owls. Providing good nesting places for predatory birds can also help control the population. However, if you go this route you probably should not be using poison baiting techniques.
Tree guards are another effective means to prevent damage to the trees. Wire mesh, perforated wire guards and plastic wraps placed around the base of the tree can be effective deterrents to meadow vole damage. However, for the tree guards to be effective for pine voles they need to be buried several inches below the surface.
Habitat modification should also be a primary mechanism to control potential damage. Voles can live in dense populations in ditch banks, rights-of-way and water ways. Closely mowing adjacent fields and burning down weeds will help prevent voles from commuting between those areas and the orchard.
Repellents on a small scale may serve to reduce damage. Materials that contain capsaicin can be applied directly to the trunks of trees. Protection is relatively short term. Due to changing chemical regulations, before applying a chemical make sure it is labeled for use in fruit trees.
Alaska vole information:
Red-backed vole - http://www.adfg.alaska.gov/index.cfm?adfg=northernredbackedvole.main
Meadow vole - http://www.adfg.alaska.gov/index.cfm?adfg=meadowvole.main