Moles can be a nuisance in a lawn or garden. They do not eat plants, but burrow close to the surface creating ridges and leaving mounds of dirt. This can making mowing difficult and detract from the aesthetic appeal of a lawn. Moles are actually a sign of a healthy lawn, however, and where possible should be left alone.
Moles mostly eat earthworms and grubs in lawns. Earthworms like moist, loamy soils. Decreasing the moisture content in the soil makes it less hospitable for the worms and grubs and therefore less hospitable to the mole. This, however, may also damage your lawn. In some cases, insecticides with Diazinon targeted against grubs may work but will also kill beneficial insects in your soil.
Trapping is one of the most effective ways to remove moles. Scissor-jaw, harpoon and choker traps are most useful. The harpoon trap works best in surface runs, where the scissor-jaw trap works better in deeper mole tunnels. Some states outlaw these traps, so check with your state government before using them. To identify the best area to set the trap, look for the straighter ridges in the grass. These are the main travel lanes, where the winding ridges indicate tunnels for foraging. To install a trap, excavate the straight tunnel and place the trap right in the middle. Backfill the soil loosely around the trap. If the trap catches nothing in two days move it to another location.
Formerly, mole toxicants consisted of the poisonous zinc phosphide in pellet form. Moles avoided this as they do not eat grains. In recent years, researches have developed gel toxicants shaped like worms, offering a more effective alternative. These worms smell and taste like the food the mole enjoys to eat and thus they are attracted to them. When they eat them, however, the ingredient Bromethalin poisons the moles. Place these, like the traps, in a straight tunnel indicating a main travel lane.
Repellents can keep moles away from certain plants in your lawn. Applying Thiram to the base of bulbs, for example, protects them from mole disturbance. Products with castor oil as the main ingredient may also help keep these critters away. Just remember with repellents, however, that they only shift the problem to another area. Follow the directions on the package for application and safety instructions.
You may also choose to simply exclude the moles from a certain area, but this is a lot of work and is only possible for a small area. Dig a trench 12 inches deep and 12 inches wide around the area you wish to protect. Cut some wire hardware cloth into pieces 24 inches in length. Bend them in half at a 90 degree angle and line the bottom of the trench with them, each one overlapping slightly with the previous. Backfill the soil, making sure the hardware cloth is completely covered and flush against the trench bottom and side. The moles should not be able to penetrate this barrier underground.