Dealing with Moles: After I-713

Mary Robson (Ret.) Area Extension Agent
Regional Garden Column January 14, 2000

However, many people dislike the appearance of mole activity in their yards and gardens. The mole-mounds are usually considered unsightly and the tunneling activities can make the yard surface uneven. Furthermore, tunneling around plant roots can stress the plants and allow avenues for invasion by meadow voles. Although moles are insectivores and eat little vegetable matter, voles are strict herbivores and readily feed on roots and bulbs of many kinds, often causing severe damage.

With the passage of I-713 in November 2000 we must re-think our mole management strategies. This initiative was passed to regulate the types of traps legal in Washington state. As of December 7, 2000, ALL traps that hold a mole's body in any way are outlawed. This includes all commercially available mole and gopher traps, which are mentioned in WSU publications on mole management. "Common" rat and mouse traps may still be used because they were exempted in the 1-713 law.

The limits of and final meaning of this Initiative will probably eventually be settled in the courts but, in the meantime, what options exist for dealing with moles?

What won't be effective against moles? Unfortunately, to date, no chemical or physical repellents, mole baits or "live traps" have proven effective on our western moles. There are many materials on the market and you can certainly try them, but they haven't been shown to be consistently effective.

There are also MANY "home remedies" that have been suggested in the past for dealing with moles but none of these that we have tested have caused any reduction of mole activity when applied in a controlled manner to a monitored western mole population. Some of these materials/treatments include human hair, pet droppings, chewing gum, cigarette butts, mole plants, mothballs, rose canes, wind-mills, pit-fall traps, etc.

Don't kill earthworms in an attempt to reduce mole activity. Earthworms are definitely beneficial garden inhabitants. Trying to remove the moles' food source is sometimes used as a control method. Unfortunately, our western moles feed mostly on earthworms and there are NO pesticides registered for earthworm control. Most lawn pesticides, including Diazinon and Dursban, are sometimes mistakenly used in an effort to kill earthworms. Applying them at more than recommended rates isn't permissible, and they do have negative environmental effects. (Both Diazinon and Dursban will be taken off the market over the next few years as the result of an EPA-sponsored action. Dursban is not to be sold after December 31, 2001 and Diazinon is not to be sold after 2003.)

So, what are we left with? The ONLY readily available treatments that approach the effectiveness of lethal trapping are:

• Underground barriers. This method entails digging a ditch 24 to 30 inches deep and burying "fences" of aluminum sheeting or 1/4-inch mesh galvanized hardware cloth. Bend the bottom 6 inches outward and allow 6 inches to extend above the ground surface. Of course, this method ONLY works if moles are not present inside the fence perimeter.

• Manual elimination. During peaks of mound-building activity one can be quite successful by flattening all the molehills and waiting for the mole to return to re-build the mounds. When the mole begins pushing up soil, the animal can usually be dug out with a spade if one is quick. Sometimes the mole can be encouraged to surface by flooding the runways with a hose but this is usually only effective in heavy soils or when the soil is already saturated (water just leaks through on sandy soils).

Hortsense: Managing plant problems with Integrated Pest Management