Moles, Voles, & Your Bulbs

Question: The bulbs I planted last fall did not come up this spring and there are tunnels running under my sod. What caused the damage? What are my options?

This is some good information, as you begin to think ahead to spring gardening.

Who could the culprit be?
Moles and voles come to mind. They are often confused with each other, but they are very different creatures and engage the environment in different ways. One main distinction that helps with identification is that voles are vegetarians (herbivores) that eat bulbs and other plants (including roots) and moles are meat eaters (insectivores) that eat worms, grubs, and other insect larva. Both make tunnels near the ground surface, but vole tunnels are not ridged and do not have mounds of soil piled up beside the tunnels. Vole tunnels have open entrances and moles create a closed tunnel system with no open entrance holes. Voles also make elaborate above ground runways, one to two inches wide, in high grass.

Mole

To determine if voles are eating your bulbs, you can use the apple bait test. This involves placing bait near a runway, covering it with a bucket with a weight on top, and waiting a couple days to see if the apple has been snacked on. For specific instructions, see the 2020 Pest Management Guide, Home Grounds & Animals from Virginia Cooperative Extension (VCE).

If the bait trap shows evidence of eating, it is most likely a type of vole called a meadow mouse or a wood rat (Microtus pinetorium). Voles have compact, stocky bodies and gray-brown color fur with short, furry tails (about 1-inch long). Their legs are short, heads are big with small eyes, and ears are partly hidden. They weigh about 1-2 ounces and are about 3-5 inches long.

Voles create specialized areas in their underground tunnels for nesting and for food storage during the fall and winter although they are active all year. Voles will gnaw on stems and bark causing damage to ornamental plants, trees, and shrubs.

They tend to live in colonies with numbers fluctuating in cycles; several generations can be moving around in a ¼ acres’ worth of pathways. They are sexually mature in 35-40 days and can have up to 6 litters per year with 2-4 pups per litter. If you’ve had vole problems in the past or have an established colony, you will want to find a way to control them as soon as possible. They can reproduce at an alarming rate.

What are your options for control?
Prevention is an easy and environmentally friendly way to control voles once they have established a colony. Try cultural methods that make the landscape less enticing to voles:

Vole

  • Switch from planting bulbs to herbaceous (non-woody) spring flowers (e.g., Johnny-Jump-Ups),
  • Keep grass mowed,
  • Eliminate dense ground cover (e.g., English Ivy),
  • Limit mulch to no more than an inch thick,
  • Remove synthetic weed barriers,
  • Clean up unused garden crops or fruit fallen to the ground,
  • Keep a 4-foot diameter free from vegetation around young trees and vines and
  • Encourage natural predators (crows, hawks, owls, or snakes) to come to your yard.

If you have a small number of voles, trapping can be effective and economical. For a small garden or lawn, place at least 10 snap-type mouse traps baited with apple or a peanut butter/oatmeal mixture near active holes.

Finally, there is the option of chemicals, which should be avoided if at all possible. Remember that restricted-use pesticides should only be used by professionals and repellents are costly, wash off in rainstorms, and must be re-applied. Please contact the Horticulture Help Desk at albemarlevcehelpdesk@gmail.com for information on repellants and the pros and cons of using them. Refer to the 2020 Pest Management Guide, Home Grounds & Animals (VCE) before proceeding with any chemical options.

References

“Moles and Voles – How to Identify and Control them in your Home Landscape,” Marshall Warren, Johnson County Horticulture Extension Agent, North Carolina State University Extension.

“Moles and Voles, Which Is Which? Who Is To Blame? What Is To Be Done?,” Lee Royer, Frederick County Master Gardener, University of Maryland Extension.

“Pest Management Guide: Home Grounds and Animals,” Virginia Cooperative Extension, Publication 456-018, ENTO-336P, 2020.

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