by Andrea Laine, EMGV

I should have known I’d have voles in my garden this Spring. Afterall, I had a mole last fall. It left behind underground tunnels. When I began to dig around in my perennial beds in March I could feel the spongy soil at the surface along the tunnel lines. A warning sign was right there in front of my eyes! But I was preoccupied with doing all the garden chores that come with spring including enthusiastically adding new plants.

A brief summary on moles vs. voles. Moles are meat eaters. They swim through the soil a foot or more below the surface and consume insects, grubs, worms, and spiders in their path. This action can disturb the root systems of plants in their way which may harm the plants, but won’t necessarily destroy the plants. Voles are vegetarians. Two species of  vole are found in central NC. I probably have pine voles  (Microtus pinetorum) which use the tunnels left vacant by a mole to reach bulbs, tubers and roots of plants, trees and shrubs to eat. Voles will also eat stems and fruits. The herbaceous plants they pick have little chance of survival. Moles work alone; voles work in groups of several adults and young.

As I continued with my spring gardening, I began to take notice of once healthy perennials and annuals suddenly showing signs of decline. Thinking it might be too hot and dry too soon in the season, I watered more, placed a shade tent over a new Sedum ‘Autumn Joy’, and hoped for the best as I turned my attention toward the myriad other tasks on my garden’s “to do” list. A short time later the plants I had on my ‘watch’ list began to flop over and reveal … the dreaded vole hole.

Strategies

Had I resumed gardening with more awareness this spring, I may have taken some strategic actions to deter voles from staying in my garden. Voles feed all year. Damage to woody plants is greatest in winter. So, better late than never – I acted in June and will keep my defenses up.  

Here are some actions to consider, beginning with those deemed most effective by Extension resources:

• Trap voles with mousetraps baited with apple slices or peanut butter. Be aware that a depredation permit is required to trap voles and you may attract and kill shrews with traps. So before expressing glee at a capture, understand how to identify between the two. Shrews have pointier snouts and shorter tails than voles. Trapping is the only way to positively identify the animal that is doing the damage. I have assumed that I have pine voles because meadow voles typically live in grassy habitats at ground level, however, meadow voles sometimes burrow underground, too.  (Distinguishing features of each are noted in the first link under Further Reading.)  When handling dead rodents and traps, wear disposable gloves and wash hands well afterward. Bury the dead rodents immediately.
  
• Invite predators. Voles live a few inches underground which provides protection from their wild predators: Snakes, owls, hawks, crows, weasels, foxes and coyotes. Building a lookout perch can help crows, hawks and owls scan the landscape for voles. I have noticed more crows than usual in my yard this year; in the future this could be a warning sign for me. Of note, a pet cat is one of the best predators of voles.
  
• Reduce their habitat. Laying three inches of mulch in your landscaped beds is great for shutting out weeds and helping the soil stay cool and moist, but it also provides great cover for voles. Woody groundcovers like juniper and fabric weed barriers act similarly. Use one-inch of mulch and commit to stay on top of weeding chores (easier said than done). Also, in the fall, rake fallen leaves away from the base of trees and shrubs.

• Protect trunks of younger trees and shrubs with wire mesh. (Guards made of other materials are not as effective.) Embed cylindrical wire guards up to three inches into the soil at the tree base. Guards should be taller than average snow level. These are easier to install at planting time, and damage to tree roots is also less likely if these are installed at planting.
  
• Get sharp. Surround new plantings with coarse gravel. And, place small piles of pea gravel around the base of fruit trees to prevent chewing by voles. This is another action that falls under habitat renovation. It dissuades voles from sticking around because scurrying around among hard material with pointy ends is uncomfortable.

• Water in a repellent.  Much like commercial sprays formulated to deter deer, rabbit or squirrels from munching on plant foliage, similar products coat the roots of plants in distasteful substances. To reach the roots, you sprinkle grains of repellent on the soil surface then water well. The repellent is made from natural ingredients.   

• There are chemical solutions termed rodenticides; they require a license to use.

It’s hard to believe that a few small rodents can do much damage to a garden, especially to established trees and shrubs. Voles are a mighty force of nature. They can kill trees by eating the bark at ground level. This is called girdling and it removes the tree’s phloem thus preventing the leaves from transporting food to the roots. Over time, the tree will die.  

Ah, but hope springs eternal. While watering in a round of vole repellent one day, I noticed a small sprig of sedum making its way through the soil surface. Evidently, some fragment of root escaped being munched by the voles and is yearning to live.

Sources & Further Reading

Reducing vole damage. This link includes illustrations useful in identifying mouselike rodents.  https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/woodland-steward/FS654_ReducingVoleDamage.pdf

https://content.ces.ncsu.edu/voles-in-commercial-orchard-and-ornamental-nurseries

https://extension.umd.edu/hgic/topics/voles

NC pesticide law and regulations:  http://www.ncagr.gov/SPCAP/pesticides/Authorit.htm https://www.epa.gov/rodenticides

About depredation permits: https://www.ncwildlife.org/Licensing/Other-Licenses-Permits/Depredation-Permit

All photos by A. Laine