Ammunition for the War on Moles and Voles
It’s one of those first warm, sunny early-spring days that invites you out to the garden. You make your way around planting beds just coming to life after a long winter but wait, where are those tulips you planted last fall? You notice, to your dismay, little trails or mounds on the soil; perhaps little holes here and there that, when examined, are too large to have been caused by heaving from the earlier frosts. If you haven’t met them before, you’re about to become acquainted with a pair of furry little critters that just love your garden, moles and voles.
LET’S GET ACQUAINTED
Voles are not the only pests responsible for runways in the garden and they’re often confused with those other fellows you’d like to get rid of…moles. Moles make two types of runways in your yard, one just beneath the surface, feeding tunnels; these are the raised ridges that you see. Others are deep below the surface and act to connect the feeding tunnels. The soil excavated from these tunnels forms the mounds distributed where moles have been active. Voles, however, leave no mounds.
While there are some similarities between moles and voles, they are very different creatures. Moles characteristically have a large snout. Their tunnels beneath the soil surface, can act to aerate the soil; moles also eat insects, grubs, and earthworms rather than plants so overall they can be considered beneficial. Moles don’t intentionally harm plants although their tunnels may dislodge roots and cause those plants to dry out more quickly. Voles are smaller than moles, about the size of a mouse. They sometimes dig tunnels, but they are also opportunists and have been known to travel about in those tunnels previously dug by moles.
In NC we have two types of voles, pine voles and meadow voles. The pine vole, (Microtus pinetorum) is becoming a bigger problem in the home landscape as increased development reduces their natural habitat and they become more adapted to our backyards, so it’s these fellows that we’ll talk about. These are the prime suspects for the missing tulip bulbs.
Pine voles are reddish brown and small, 2-4 inches long, with a short tail, blunt face, and tiny eyes and ears. They feed mainly on roots and tubers of plants (think tulip bulbs). They spend much of their time under leaf litter or in their underground burrows. They don’t hibernate and even though we rarely see them, they are active day and night. Their lifespan averages anywhere from 2 to 16 months. A pair of voles can have up to 6 litters a year with 2 to 4 young per litter; at 35-40 days, the young female is ready to produce her first litter. Pine voles are monogamous and family units tend to maintain territories as small as 1000 square feet and remain there for their entire short lives. They have admirable family values but we still begrudge the little varmints. So, you can see, when they arrive and set up housekeeping in your garden, you’d be wise to step up to (or on to) the challenge.
In the ongoing wars to protect the gardener’s tender and precious plantings from the ravages of voles, a myriad of attack weapons have been developed, humane and otherwise. Just check out the shelves of your favorite lawn and garden store, or the on-line catalogues; these include repellants (short term results only), devices (don’t work), rodenticides (designed to kill mammals…think pets), baits and traps. The extent of plant loss or damage in relationship to vole populations should be considered when choosing which way to approach the problem. Safe and non-toxic methods like exclusion (installation of underground physical barriers) have proven to be effective because voles aren’t fond of getting cut or injured. These methods generally don’t involve chemicals and are safe to use in the presence of humans, pets, and wildlife. However, reduction in natural vole habitat also reduces habitat for the their natural predators, owls, hawks, snakes, etc. These predators depend on rodents as a food source and possess sensory abilities for locating their meals.
We know and are grateful for the fact that voles are not fond of daffodils. But, when you try again (and you will, you know) to develop that lovely bed of tulips or other savory plantings, you might want to try a safe and humane approach. Incorporating coarse particles like expanded slate into the beds has proven to be an effective barrier to pine voles. Hardware cloth (less than a 1⁄4 inch mesh) can be used also but may eventually restrict root growth in larger plantings. Some have found it helpful to mix sharp-edged pea gravel throughout the soil as they prepare a new planting bed. Products such as Perma-Till and VoleBloc can be useful deterrents when used in this way. While not inexpensive, these methods do not pose ongoing risks to the environment or to the neighbor’s favorite pet.
Celeste M. Bissell is President of the Extension Master Gardener Volunteers at North Carolina Cooperative Extension in Lee County.