Moles, voles, mysterious holesBy Sally G. Miller (sallyg)
April 28, 2010
Moles and voles rarely show their faces, but the evidence left of their different digging styles shows which of these garden foes is present in your yard.
Raised soil ridges, excavated earth and stripes of dying grass: suspect # 1, the bumbling "blind" mole
Typical mole damage consists of raised ridges of soil, about an inch high and four inches wide, traveling under turf or through garden beds. These raised tunnels are made by moles in search of a meal. Moles eat insects, favoring grubs and worms. What moles lack in visual acuity (moles are not actually blind) they make up for in digging ability. Moles use their strong front feet and impressive claws to make extensive networks of burrows. The shallow tunnels they dig are the ones that annoy gardeners; as moles tunnel, they heave up grass and plants and cause their roots to dry out. Some shallow mole tunnels are used just once. Press fresh mole tunnels down. Grass might recover from a brief upheaval. Lawn areas may even reap a slight benefit from some mole activity if the moles are eating the grass-damaging grubs of Japanese beetles.
Neat holes. unexplained plant failure and suddenly wilted individual plants: suspect #2, the voracious vole
Voles look like mice; some are commonly called meadow mice or pine mice. Voles may travel through mole tunnels, but also dig their own burrows. The only visible evidence of a vole burrow is the neat exit holes an inch or two across. Vole holes can be right out in the open, or cleverly hidden under foliage or debris in the garden. Deep mulch and areas of groundcover plantings offer excellent vole habitat. Voles eat plants, and are far more destructive in the landscape than moles. Voles can travel above ground but really prefer to stay hidden. They may make pathways just under mulch, matted leaves, boards or snow; just about anything laying on the surface of the soil will make a nice roof for a vole run.
Voles are rodents, with front teeth designed for gnawing. All parts of plants can be vole food. Since voles like to work under cover, it's the undergound parts pf plants that bear the brunt of the vole's foraging. Bulbs, fleshy roots like those on Hostas, and tree bark at the soil line all fall victim to voles' appetites. A favorite trick of the vole is to eat the roots of a plant without disturbing the top growth at all. Many vole-plagued gardeners have gently lifted the leaves of a "sick" plant, only to find the roots have been completely eaten away. A previously unseen tunnel leads right to the stricken plant.
Mole and vole control: starting with gentle, ending with lethal
Consider these steps to control voles or moles in the garden.
These critters like to be hidden and undisturbed; disturb them! Keep grass mown, and get rid of tall weeds. Tidy up the garden and remove debris. Cultivate and work around your plants. If voles are snacking in your compost, move it away from prized plantings, or use the bokashi method on kitchen scraps. Treat the lawn to reduce grub infestations, which in turn may make moles move away in search of more plentiful food sources.
You can try to make the garden unpleasant for the critters with commercial repellant products or home remedies (and you can spend hours at the computer reading testimonials from homeowners who've tried these products.) The bottom line from university fact sheets is that repellants do not have lasting proven results, although one university source gives mild approval to castor bean oil treatments for moles.
Some repellants try to make the garden too stinky for sensitive little noses. Rodents like voles are said to hate peppermint oil; tell that to the voles currently using my mint patch as a front porch. Other products not specifically sold as critter repellants have been spread on the garden or inserted in burrows by many a desperate housewife. These include mothballs, ammonia, Milorganite fertilizer, blood meal, and used cat litter. Certain plants have a reputation for driving away moles and voles. Those species are Castor bean (Ricinus communis), marigolds, daffodils, edible and decorative Alliums (onions) and caper spurge (Euphorbia lathyris or mole plant.) You'll want to educate yourself about these plants before committing to growing them; some come wth their own bad habits or even safety risks. Devices that create vibration or magnetic waves underground are another angle in critter control. Here's a cute one, the Solar Moler. Again, all I can say is that university research fails to find poof that these work.
Use physical barriers
Barriers can protect your best specimens and force the foes to find a meal somewhere else. Use 1/4 inch hardware cloth to make a basket of sorts to protect the plant's root mass from tunneling from the sides and below, and extend the wire several inches above ground to be sure persistant critters don't just "hop the fence." Voles might be deterred from digging into a plant which is installed with a hefty dose of stone around the planting hole. PermaTill/ VoleBloc is sold as an amendment to improve poorly drained soils and for this barrier concept. Solid wood or stone barriers to two feet in depth should keep moles out. Of course, if you make a perimeter barrier around a large yard, moles or voles could find a way over and set up housekeeping completely within your "protected " zone.
Housepets, and wildlife such as owls, snakes and foxes, can help keep garden foe populations in check but won't kill every last vole or mole.
Get serious with poisons or traps
Rodent poisons work well on voles (not moles; moles aren't tempted by the grain in rodent bait.) Be aware that rodent poisons are also toxic to people, pets, and other wildlife. Use caution and follow directions. Juicy fruit gum iand castor beans placed in mole tunnels are "clever" ideas from home gardeners, but do not have reliable research backing up their effectiveness.
Traps are effective for moles and voles. Use the correct trap for each specific animal and follow all directions.
Voles are very damaging to plant material. Moles are more benign but also can cause problems in the landscape. Good maintenance practices are important in keeping these vermin in check. When they reach intolerable levels, trapping is probably the most effective way to reduce the population.
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