Don’t let voles get the best of your garden

By Julie Riley

I have a meadow vole apartment complex in my back yard and a front lawn decimated by red-backed voles. I see them scampering brazenly across the lawn in broad daylight. They are supposed to stay hidden in tall grasses. Alaska voles eat broccoli and juggle zucchini. I am worried about my snow peas.

A few years ago, I bought a live trap to get a better look at these creatures. The trap was big enough to catch a squirrel. I caught a vole and took him over to KTVF hoping he’d get a spot on the Channel 11 evening news garden report but the little guy did not become a television star. Needing to further my vole education, I visited Alaska Department of Fish and Game’s website. I learned there were four species that could possibly be terrorizing Fairbanks gardens and yards.

Meadow voles dig underground burrows. I use the name meadow voles generically to include all of the Interior Alaska Microtus species, the meadow vole, tundra vole and yellow-cheeked vole. These voles are found in grassy habitats in colonies of up to 300 individuals. The other vole found here is the northern red-backed vole, a smaller mammal that lives in small groups in the forest or in meadows. It does not burrow or build runways but will use the runways made by meadow voles.

Finding meadow vole burrow holes in vegetable and flower gardens implies they are the culprits nibbling lily bulbs and beets. But meadow voles are supposed to eat primarily grasses and seeds. It’s the northern red-backed vole whose diet is more diverse. I need a gardening vole biologist who can shed some light on this vole-in-the-garden behavior.

Where there are voles in the garden, there are gardeners devising ways to reduce their populations. I’ve seen an entire raised bed surrounded by a moat of plastic containers. A big-hearted gardener at the Fairbanks Community Garden once confessed she put a raft of sticks in a water-filled pitfall trap in her neighbor’s plot. Although not in favor of voles running about, she felt drowning an inhumane way to go. I thought it best not to mention the vole popsicle I found in my watering can the previous September.

That vole had run across asphalt, cement and gravel to gnaw on my potatoes. I had tried to no avail to thwart this activity with closely spaced shish kabob skewers. Usually hardware cloth is used to exclude voles from the garden. Research at the University of Nebraska Lincoln found the material to be effective when sunk 6 inches deep and extending at least 10 inches above soil line. I wouldn’t bet my giant cabbage this barrier would keep voles out. The northern red-backed vole is known to climb trees.

This study also looked at vole repellents. Almond, garlic and spearmint oils were ineffective. Capsaicin was also not an effective repellent when used at 0.5 percent. This substance that makes chili peppers hot worked as a repellent in other studies but it needed to be reapplied every two weeks.

In Fairbanks most of the vole repellents on the market contain castor oil. Applied full strength, castor oil effectively repelled captive voles in the Nebraska study. Dilution rates of 0.65 percent and 16 percent did not work. Other products with repellent properties registered in Alaska contain fir needle oil, coyote and fox urine. Repellents cannot be applied to food crops unless specified on the label.

There are numerous rodenticides registered to kill voles. Some can be utilized by home gardeners. Others are restricted use products that require a professional certified applicator. Before purchasing any pesticide, read the label carefully. Many anticoagulants baits are not effective unless fed on by voles for at least five days. Some products must be placed 100 feet or more away from the house.

If you decide to use snap traps, consider investing in hefty models such as those made by Tomcat. Set the trap near a burrow entrance and cover both with an overturned 5-gallon bucket. Place a large rock on top of the bucket so that pets can’t access the trap. Birdseed, grass seed and rolled oats can be sprinkled on the ground as bait but it’s not necessary. Because of pathogens and parasites, gloves should be used when removing voles from the traps.

I think the perfect trap for handling my high vole population is a multi-catch live trap. They are supposed to be able to capture as many as 15 voles at a time. I’ve put one on my birthday wish list.

Julie Riley is the horticulture agent for the University of Alaska Fairbanks Cooperative Extension Service in the Tanana District office. She can be reached at jariley@alaska.edu or 907-230-7339.