Voles or Moles?

By: Peter Martin

The wrong identification can make or break an account.

Distinguishing between vole and mole damage can be tricky. Both pests construct tunnels, which can result in lawn and garden damage. Moles frequently get the blame for these landscape eyesores, but the real culprit may, in fact, be voles.

Erroneously referred to as meadow mice, voles are rodents. By contrast, moles are insectivores with completely different diets and behavior. Even the damage they wreak on lawns and garden has a distinctive look. As always, properly identifying the pest (mole or vole in this case) can be the difference in a pest management program that works and one that is a continued source of frustration.

That was the dilemma technicians at JP Pest Services in Milford, N.H., faced this summer when they were asked to manage pests that were decimating showcase gardens at a large food manufacturing facility.

As the focal point of the manufacturer’s main courtyard and public tour area, the landscaped gardens typically were resplendent with colorful summer flowers and shrubs set against dark, green junipers and lush lawns.

Vole damage (Bell Laboratories Inc.)

An on-site horticulturist designed the grounds, which were maintained by a local landscaping company. What was a landscaper’s paradise turned nightmarish as day after day newly planted flowers were eaten and lawns marred by tunneling.

With losses mounting to thousands of dollars, the landscaper sought help from JP Pest Services, which had handled the facility’s interior and exterior perimeter rodent management services for more than a decade. Besides having certified applicators, JP Pest Services offered a wildlife department, which it started last summer to deal with mole problems.

INSPECTION FIRST

Gary Nielsen, an entomologist and troubleshooter for JP Pest Services, inspected the grounds. In addition to severed flower stems, he found visible runways and tunnels. He also discovered signs of trouble from last winter — chewed bushes and girdled stems — though the real trouble started in mid-May when flower beds were planted and mulched.

“We do structural pest management and had just started doing mole work last season, but this was beyond our strong suit and unlike any mole damage we’d seen,” Nielsen recalls.

With a lot at stake, Nielsen consulted with Sheila Haddad, a Bell Laboratories technical representative, for a second opinion. Was it voles or moles? And, what was the best product to use?.

VOLE VERSUS MOLE DAMAGE

Visible identification of the two pests is difficult because moles rarely appear above ground. Voles, on the other hand, freely travel in and out of their tunnels.

“There had been some sightings in the early morning and evening at the facility, but they never had vole problems before,” Nielsen notes.

He and Haddad next took a closer look at the damaged plantings. Both moles and voles can damage plants.

With moles, above-ground plant damage results from injury to roots during their constant burrowing and tunneling. Moles are insectivores and prefer to eat earthworms and grubs.

Voles, on the other hand, are voracious herbivores with an appetite for green vegetation in warm months and bulbs and tubers in winter. They also gnaw bark at the base of trees and shrubs.

“Voles are pretty voracious,” Nielsen says. “A mature female can decimate a bedding. We had one 6-foot-by-6-foot plot and every single plant was gone, probably by one vole. With green plants, you have to eat a lot.”

Plants put in on Friday, he says, would be gone on Monday. He also notes that voles, like lemmings, like to cut vegetation and make hay. They’ve been known to clip grass and other plants at the base and drag them into bait stations to dry and eat later. Sure enough, Nielsen and Haddad found flowers that were chopped off and dragged into juniper bushes and into tunnels.

THE TUNNEL TIP-OFF

An inspection of the tunnels on the facility’s lawns revealed the final clue.

Moles are solitary creatures that spend their lives digging tunnels underground in search of food. They create two types of tunnels, each with a distinct appearance above ground:

1. Surface runways, which appear as raised, brown grassless streaks and can be either long and straight, or shaped like a spider web.

2. Deep tunnels, which are evident above ground as “mole hills.” They’re created when moles push soil and debris to the surface. These mounds are a sure bet of mole problems.

Voles, however, create well-defined tunnels or surface runways about 2 inches wide, with clearly visible entry and exit holes to their burrows. Runways form as voles eat grass and scurry back and forth from their tunnels.

Voles will take advantage of abandoned mole tunnels but, when Haddad and Nielsen found clearly marked opening and exit holes in the surface runways, they rightly concluded the problem was voles.

Mole Damage

VOLE CONTROL WITH ZINC PHOSPHIDE

For fast control, Haddad suggested baiting tunnels with Rodent Rid, Bell’s pelleted bait containing zinc phosphide.

“We pride ourselves on using the least-hazardous materials (Class III or IV), but the nice thing was that the active ingredient (ZP) was deactivated by water and moisture,” Nielsen says. “We didn’t have to go back to pick up bait, either.”

With New Hampshire experiencing one of its rainiest summers in years, certified technicians hand-baited the restricted-use pesticide three days a week for four weeks. Once they located active burrows, they poked holes in the ground, applied a teaspoon of bait, then covered the holes. Sprinklers were turned off on the Mondays, Wednesdays and Fridays when they baited, giving the pelleted bait a chance to work. On off days, they were turned on to keep flowers from dying. By the end of the second and third weeks of baiting, results were evident.

“We collected at least a dozen dead voles above ground, and some died underground,” Nielsen says. “The company was pleased with the results, especially that we could get a handle on it quickly so they could re-plant.

“This was a first in our history with the company,” he concludes, “and it paid to know the difference.”

You can reach Martin, technical director for Bell Laboratories in Madison, Wis., at 800-333-6628, or e-mailtech0001@talpirid.com .