I hear the exasperation from homeowners several times a week in late winter and early spring. Their lawns will be littered with piles of soil that seem to appear out of nowhere. Voles are often blamed, yet an unrelated culprit known as moles are the really enemy in turf wars.
Moles, voles, schmoles, you may be saying. Knowing the difference, though, is critical in your approach to regaining control of your landscape. In short, moles are carnivores, meaning they eat meat. Voles are herbivores, meaning they eat vegetables. Voles devour roots, bark and lower vegetation, but rarely eat grass and their tunnels are rarely a big issue in the soil. Moles, on the other hand, just bomb about underground in search of whatever grub, worm or insect they can find.
When people ask what to do about moles, I often respond by telling them to cheer, “Go moles, go.” Moles eat the white grubs that become Japanese beetles and June beetles. In the big picture, these grubs and beetles do far more damage than moles to the overall landscape. Grubs damage grass roots; the beetles devour foliage of landscape plants.
“White grubs, in many locations, are the leading pest of grasses by far,” said associate professor Albrecht M. Koppenhofer, an entomologist from Rutgers University in New Jersey. “They can cause significant damage in certain situations, but people also should not overreact the first time they see a grub in the soil.”
Voles — These are the true varmints of the garden. They want your plants, plain and simple. If you’ve ever lost a fruit tree to girdling at the base, or a prized perennial that was chewed from the roots and left for dead, voles were the likely suspects.
Often called pine and meadow mice, the pine vole, Microtus pinetorum, and the meadow vole, M. pennsylvanicus, have become huge problems, especially in the East. Development has taken away their natural forest habitat, and also their natural predators, including fox, bobcat, weasels, snakes, owls and hawks.
Pine voles are reddish brown and small, about two to four inches long, with a short tail, blunt face, and tiny eyes and ears. Meadow voles are more gray in color. Both have tiny, yet prominent, sets of eyes. Because voles don’t hibernate, they feed year round on roots and underground stems of plants. They can tunnel on their own, but often borrow tunnels already burrowed by moles — thereby creating even more confusion among homeowners. If you find exit holes on the tunnels in your lawn and garden, chances are you have voles, not moles, since moles are blind and only come up for daylight by mistake.
Moles — When you see a mole close up, the differences from voles are obvious. Take one look at the webbed front paws and claws of the mole and you’ll instantly see why many texts refer to the critters as “master excavators.” They are also prodigious at the dinner table, able to eat up to their full body weight within a 24-hour period. Unlike voles, which travel in family packs, moles often live and work alone. They are also more active after sundown.
Their damage is usually fairly minimal; the displaced soil can easily be smoothed out with a metal rake. If you feel you must be rid of the moles, soaking the ground with castor oil will help, but the easiest way is to work on eradicating the source of food. In other words, get rid of the grubs and the moles will soon tunnel elsewhere.
The most effective natural way to control grubs is to apply microscopic organisms — known as beneficial nematodes — to the soil in May through early June or late August through September depending on your location. This timetable can vary greatly in warm-season climates and if you suspect grubs as a problem on your lawn, you should contact your local Cooperative Extension office to determine the insect’s lifecycle in your area. The Extension agent should also be able to point you toward a local source for the nematodes; Koppenhofer, at Rutgers, and many other scientists are constantly updating information on strains of the nematodes that work the best in certain climates against specific grubs.
The keys to success with beneficial nematodes are two-fold: 1) Be sure you have a treatable problem and 2) get the timing right. As a general rule of thumb, if you have five or fewer grubs per square foot on your lawn, you do not have a significant problem. You can test this by simply digging a square foot of soil to a depth of six inches. Break apart the soil and sod and count any grubs you find.
“A few grubs are a part of the natural system and people shouldn’t panic,” said Todd Harrington, the oft-cited natural lawn care professional from Connecticut. “In a healthy lawn with a healthy root system, I rarely see a grub problem worth taking action.”
If you do act, timing is everything. Grubs spend about 10 months of the year in the soil and two months of the year as adult beetles in the landscape above ground. Trying to kill the grubs just before they emerge from the soil in late spring or just after they lay eggs re-enter the soil in early autumn is paramount. Treating at other times won’t help a bit, whether you use a synthetic chemical or beneficial nematodes.
Applying beneficial nematodes is an easy, non-toxic exercise. You’ll need a device for your garden hose known as a hose-end sprayer and at least enough hose to reach all infected areas of your property. Further directions on mixing and application will be available from the nematode supplier.
One other treatment — You can also inoculate your lawn and garden with a white powder known as milky spore disease, but this usually takes two to three years to build up enough population to be fully useful. This product, according to Koppenhofer, has shown “highly variable” results.
“Since the commercially available strain of milky spore disease is ineffective against white grubs other than the Japanese beetle,” he said, “applicators who are interested in using milky spore disease should first make sure that their grubs are actually Japanese beetle grubs.”
One Other Note — Yes, it’s true the same poisons that rid homes of mice will also work to kill moles and voles When the snow melts this spring and you see tunnels and dead plants galore, you may be tempted to take out the toxins. In a word, don’t. These poisons, left in the open, will be fair game for every cat, dog, bird and child in the neighborhood.
Next week, I’ll provide more information on vole control.
Paul Tukey, January 19, 2006.
