Moles: the ridges, the mounds, and what actually gets rid of them

Here is the part almost every homeowner gets backwards. Moles are not eating your grass. Iowa State Extension puts it plainly: the main mole meal is earthworms, supplemented with some insect larvae, centipedes, millipedes, and spiders. Rutgers describes the diet as mainly earthworms, white grubs, crickets, and other invertebrates, and notes that moles rarely consume plant material. When plants do get chewed inside a mole tunnel, Rutgers says it is usually mice or voles using the runway as a free highway.

So the damage is mechanical, not appetite. A mole hunting worms just under the sod lifts the turf as it goes, and that lifted strip is your ridge. Nebraska Extension says a mole may burrow as fast as a foot per minute making surface feeding tunnels, and Iowa State puts surface runs at 1 to 3 feet per minute. That speed is why one animal can make a whole lawn look overrun. It has to keep moving: Nebraska and Rutgers both say moles eat 70 to 100 percent of their own weight daily.

The cone shaped mounds come from a different tunnel. Those cap the deep permanent runways, which Rutgers places 3 to 12 inches below the surface, and the mole pushes excavated soil up a vertical shaft, which is why the plug sits in the middle of a round pile. Iowa State separately notes that winter activity happens in deep tunnels 6 to 24 inches down, so the lawn can go quiet in cold weather without the mole going anywhere. Iowa State also notes the difference that matters for trapping: surface feeding tunnels may be used only once, while main runways may be used for years.

Start with the myth, because it costs people the most money. Iowa State Extension calls grub insecticide for mole control the great landscape lie and states flatly that applying insecticides for grubs will not solve the mole problem, because earthworms are the primary food. Rutgers says grub control will not provide much long term relief, and that even if moles temporarily leave a treated area they will not move far and can reinvade the site years later. Nebraska calls soil insecticides expensive, with no immediate reduction of damage and little likelihood of long term control. Having moles does not mean you have grubs.

What extensions do agree on is trapping. Nebraska calls trapping the most effective and practical means for controlling problem moles. Minnesota Extension says most experts agree trapping is the most effective way to control moles, and names the harpoon style trap as the easiest to set and most readily available. Rutgers describes harpoon, scissor jaw, and choker loop designs, and says that unless mole activity is very light, multiple traps (it gives 3 to 5 per acre) give better and faster control than a single one. Nebraska recommends using at least three. The rule that decides success is placement: set on a straight permanent runway you have confirmed active with the flatten and recheck test, not on a meandering feeding tunnel.

Repellents are weaker than the marketing. Rutgers says castor oil products are supposed to reduce activity when watered in, but that no scientific research has shown consistent results. Nebraska rates castor oil products as minor in effectiveness, citing one study where a product reduced activity for over 30 days. On electronic and vibrating devices, Nebraska says none has been proven effective, and Iowa State groups sonic devices with the things that do not work.

Baits are murkier. Iowa State says poisons and gassing do not work, and Rutgers notes poison peanuts and other grain baits are ineffective because moles eat insects and earthworms, not grain. Nebraska notes that bromethalin based synthetic worm replica baits have drawn numerous positive reports but says more rigorous testing of those products is needed, and does not recommend them on the strength of those reports. Follow the product label and your state's regulations for any mole product or trap. The label is the law.