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If there were moles in the Garden of Eden they must have changed their habits since then. Nothing piques a gardener's ire more than evidence of these inveterate diggers: damaged turf, uprooted plants, undermined patios and random piles of dirt.
However, other pests cause similar damage so it's important to study the suspect's modus operandi:
1. Small round holes in the ground, surface or slightly subsurface runways, teeth marks on vegetables or berries (or produce disappearing), chocolate brown scuttling critters, no raised turf--vole
2. Sizeable rounded crescent or horseshoe-shaped mounds (often several) with plugged entrance holes, missing plants or roots, no raised turf--pocket gopher.
3. Holes (no mounds) in turf or under and along walls, foundations and woodpiles, missing plants and berries, no raised turf--striped gopher or chipmunk.
4. Conical mounds (sometimes absent), meandering ridges of raised turf or soil (soft when stepped upon) plants undermined or pushed from the ground but not eaten, a few small holes--mole.
Many ways have been devised to reduce or eliminate mole damage but researched-based studies show that some work better than others and a few are entirely ineffective.
Repellents: Castor oil based repellents are readily available. Reports of their effectiveness are mixed. Here are links to conflicting opinions:
http://ohioline.osu.edu/w-fact/0011.html
http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=92
Most experts agree that many commonly touted repellents are ineffective including chewing gum, ultrasonic devices, bleach, mothballs and human hair.
Poison baits: "Poison peanuts��? sold to control moles and gophers are not effective according to University Extension and other wildlife specialists because moles (insectivores) are unlikely to recognize them as food. Recently introduced poison products formulated to resemble mole food (earthworms) may be more effective. Read about them at http://agebb.missouri.edu/hort/meg/archives/v11n6/meg2.htm
Grub control: The theory is that moles will vacate yards and gardens devoid of soil insects, especially grubs. However, studies indicate that moles eat more earthworms than grubs and because maintaining insect free soil is a challenge, results may be mixed at best.
Smoke bombs and fumigants: Mole tunnels are complex systems so multiple simultaneous and repeated bombing may be needed to get results.
Trapping: Most experts agree that trapping is the best way to control (not eliminate) moles. Unfortunately, many who try it give up because they haven't gotten results. Trapping success requires practice and persistence. Harpoon traps are readily available and easier to set than others on the market. Here are tips to improve trapping skills: http://www.extension.umn.edu/yardandgarden/ygbriefs/W703moletrapping.html
-Bob Bystrom, Master Gardener