Managing Mole Problems Without Pesticides

Townsend's Mole

By Caroline Cox, 2004; Updated 2019

Moles are beloved. Remember the friendly Wind in the Willows character in the black velvet smoking suit who abandoned the spring cleaning of his underground home for the freedom of life on the river? And yet moles are also hated, especially when their mounds pop up in a newly planted garden or next to prized roses. Whatever your feelings about moles, hate or love, pesticides are not a necessary part of solving mole problems. Here’s the information you need to manage moles without poisons.

Northwest Moles

Three species of moles cause most of the problems for lawns and gardens in the Pacific Northwest. The Pacific or coast mole is found in drier and more woody habitats [1]; the Townsend's mole (the largest mole in North America) west of the Cascade mountains [1]; and the broad-footed mole in southern Oregon and into California [2]. The same general procedures are used for managing all three.

Mole Facts

Moles are digging machines. Their bodies are streamlined, and they have powerful forelimbs for moving soil. They even have large lungs and special blood to help them survive the oxygen-poor conditions underground [4].

Moles stay underground most of their lives, except when juveniles need to look for a new home. They return home if they’re moved; moles have crossed canals, paved roads, and even a river in order to get home [4].

Moles eat mostly earthworms and insects along with small amounts of plants, especially grasses [3].

A single mole can build many mounds: one Oregon mole built over 300 mounds in 11 weeks [3].

Benefits

Moles are significant contributors to soil ecosystems: “their tunneling and mound-building activities aerate and mix soil layers and provide drainage. Moles also eat large numbers of insects, insect larvae, and other pests” [3].

Moles or Gophers?

Pocket gophers are often confused with moles, and require different management techniques. Examine the mounds in your yard to be sure that they were made by moles. Mole mounds are volcano-like, circular, and usually made of cloddy soil. Gopher mounds are flatter, fan-shaped with dirt thrown in one direction, and are made of finer soil [5]. In the Northwest, moles are more common west of the Cascades [5] and in areas of California with moist soils [6].

Live with Moles

Since moles have an important ecological role, it’s often worth trying to live with them. In a yard with few moles, or in a relatively small yard, a team of British biologists suggests simply raking away the mole mounds whenever they are formed [7]. This means that they aren’t detracting from the appearance of your yard, and that there’s less chance of weed seeds germinating on the disturbed soil [7].

Don’t Encourage Moles

Moles appear to prefer grassy areas over areas with lots of broad-leaved plants. The team of British biologists mentioned above tried removing grass to see if the number of mole mounds in a grassland would change. They found that moles built fewer mounds in plots where they had removed grass than in grassy plots. This kind of experiment has not been done with Pacific Northwest moles, but it suggests that you might want to try planting something different if you have a lawn with persistent mole problems.

For lists of native ground covers that can be used as replacements for grass, visit https://www.nwcb.wa.gov/groundcover-alternatives-for-western-wa (for western Washington), or https://extension.oregonstate.edu/sites/default/files/documents/1/nativeplantreclist.pdf (for western Oregon).


Mole mounds

Trapping

“Trapping is the most effective choice for mole control when it becomes necessary” [8], according to a publication for landscape professionals produced by Seattle Public Utilities. The University of California Statewide Integrated Pest Management Program agrees, describing trapping as “the most dependable method of mole control” [6].

Of course there are other opinions about trapping, with some believing that it is inhumane to moles. In Washington, "body-gripping traps" like the scissor-jaw trap recommended below are unlawful for trapping wild animals, unless a special permit is obtained [9].

Consider how you feel about these issues if your mole problem seems to warrant trapping. If you decide you want to trap your moles, follow these recommendations:

  1. Use a scissor-jaw or harpoon type trap [6].
  2. Trap in a main underground tunnel that is used frequently (about 8 to 12 inches below surface), rather than a shallow surface runway that is used temporarily for feeding. To determine this, tamp down short sections of runways and mounds. Observe daily and make note of frequently used, active areas [6].
  3. Set traps only in runways used most frequently, and at least 18 inches from a mound. Locate deeper tunnels by probing near a mound with a pointed stick or metal rod, until you feel the soil suddenly give way [6].
  4. Prepare the trap location by using a trowel or small shovel to remove a section of soil slightly larger than the trap width [6].
  5. Build a soil plug in the center of the runway for the trigger pan to rest on [6]. 
  6. Place the trap, with the safety catch set, into the tunnel. Wedge it firmly, so that the trigger sits snugly against the top of the soil plug. You can scatter loose soil over the trap so that light doesn’t enter the part of the tunnel you dug out [6].
  7. Release the safety catch [6].
  8. Once trapped, handle dead animals with a plastic bag on your hand. Turn the bag inside out over the mole, and tie the bag shut [10].

Repellents

NCAP does not recommend the use of pesticides. However, there are plant-based castor oil mole repellents that, according to the U.S. Environmental Protection Agency, do not pose known health or environmental hazards [11]. Castor oil is extracted from seeds of the castor oil plant and can be used as a medicine. The seeds are highly toxic because they contain the poison ricin. The oil contains small amounts of ricin [12].

Castor oil has been found to have some effectiveness as a repellent for eastern moles, but has not been tested for Northwest moles [6]. Information about castor oil mole repellent is available at https://www.bonide.com/trusted-brands/molemax/

Ineffective Methods

There are various "home remedy" methods that have been suggested for dealing with moles, however their effectiveness has not been proven. These ineffective methods include: mole plants, chewing gum, mothballs, household lye, broken bottles, laxatives, automotive exhaust, smoke bombs, predator urine, and electrical devices that vibrate the soil [6], [8], [10].

Conclusion

Remember that moles are an important part of soil ecosystems. Try to live with them. If your mole problem exceeds your tolerance for them, pesticide-free techniques for killing moles are effective. 

References & Additional Sources of Information

  1. Washington Department of Fish and Wildlife. Undated. Living with Wildlife: Moleshttps://wdfw.wa.gov/species-habitats/living/species-facts/moles#
  2. Nevada Department of Wildlife. Undated. Broad-Footed Molehttp://www.ndow.org/Species/Furbearer/Broad-footed_Mole/
  3. Verts, B.J. and Leslie N. Carraway. 1998. Land Mammals of Oregon. Berkeley: University of California Press. Pp. 68-72.
  4. Hartman, G.D. and T.L. Yates. 2003. Moles: Talpidae. In Wild mammals of North America: Biology, management, and conservation. 2nd edition. G.A. Feldhammer, B.C. Thompson, and J.A. Chapman. (eds.) Baltimore: The Johns Hopkins University Press. Pp. 30-55.
  5. Washington State University Cooperative Extension and Oregon State University Extension Service. 2008. Sustainable Gardening: The Oregon-Washington Master Gardener Handbook. EM 8742.
  6. University of California, Agriculture and Natural Resources. 2004. Pests in Gardens and Landscapes: Moleshttp://ipm.ucanr.edu/PMG/PESTNOTES/pn74115.html
  7. Edwards, G.R., M.J. Crawley, and M.S. Heard. 1999. Factors influencing molehill distribution in grassland: implications for controlling the damage caused by molehills. Journal of Applied Ecology 36:434-442.
  8. Seattle Public Utilities. Undated. Integrated Pest Management for the Landscaping Professional: Moleshttps://www.seattle.gov/Documents/Departments/SPU/MolesIPMFactSheet.pdf
  9. Washington Department of Fish and Wildlife. 2019. Furbearer trapping seasons and rules. https://wdfw.wa.gov/hunting/regulations/trapping
  10. Oregon Metro. Undated. Moles, voles and gophershttps://www.oregonmetro.gov/tools-living/yard-and-garden/garden-problems/moles-voles-and-gophers
  11. U.S. Environmental Protection Agency. 2001. Plant Oils Fact Sheethttps://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_G-114_01-Jul-01.pdf
  12. Centers for Disease Control and Prevention. 2018. Facts About Ricinhttps://emergency.cdc.gov/agent/ricin/facts.asp

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