They're Baaaaaaack! Voles.

Posted by Alison O'Connor, Larimer County Extension

Well...to be honest...the voles may not be back so much as they never really left. We've blogged about voles before. Tony blogged about them in the lawn, and Irene blogged about them too--twice!

Meadow vole. Kinda cute, but crazy destructive.

Voles are small, mouse-like creatures with short, stubby tails. They are sometimes called meadow mice and we have eight (8!) species that live in Colorado. They are most active at night, but you will see them during the day--and like mice, they will run frantically when disturbed. You'll see damage in the lawn with their tunnels and also on landscape plants that they chew.

Vole tracks in the lawn.

The good news is that voles are a boom and bust species. We'll see huge populations one year, and the next season they will crash. Our state veterinarian once told me that some species of voles do their part to help control populations--male voles will become sterile when he has too many siblings. Fascinating.

They do have natural predators, like birds of prey, coyotes, and fox, but there seems to be so many voles and too few predators. Plus, voles love our landscapes where there aren't a lot of predators and it's a cozy, safe place to take residence. And that's where they are a problem. They like to live in tall grassy areas, and also in landscape beds--especially those with mulch and landscape fabric.

Voles love to live under landscape fabric, because it's safe from predators.

I visited a friend's landscape in Berthoud recently and over the winter, when voles were actively feeding on her plants, she ended up losing most of her roses, some lavender, and a few perennials. She literally just pulled the plants from the ground. Voles love to chew at the base of many ornamentals and fruit trees, girdling them. In the case of my friend, they chewed so much, the plants just broke off at the base.

All of her roses were killed this winter.

Girdled rose chewed by voles.

It's especially upsetting, since we all know that landscape plants are an investment. Losing this many can affect the budget--plus, the plants were mature and her landscape was beautiful last summer. The one that really got me was her fantastic dwarf blue spruce...which still looks perfectly healthy, but it's only a matter of time before it goes into decline. When you have the entire base of the tree that's been girdled, there's no way for the tree can move water and nutrients up and down the tree, since the xylem were damaged.

What looks like a perfectly healthy dwarf blue spruce...

The base of the spruce was girdled completely, approximately 2-3" off the ground.

Another sign of voles is damage to junipers. Voles love junipers--it must be their form of chocolate. I received an email earlier this week from a client who wanted to know what caused the browning in his junipers. I suspect it's voles and asked him for confirmation.

Potential vole damage in junipers.

Trace back the branches to the base and look for chewing where those branches attach to the shrub. The only remedy in this situation would be to individually (and painstakingly) cut out each damaged branch. Oh, and control the vole population.

What works best are unbaited mouse traps, placed end-to-end, near areas of activity and cover with a piece of gutter. Voles aren't smart animals and they will run, with free abandon, throughout the landscape. If you place the traps near active tunnels or near where they are actively feeding, you'll snap them, just like mice. Traps need to be checked and reset daily. There's lot of recommendations of baits that you can use (including Juicy Fruit gum!?!) but voles aren't motivated by baits--they are herbivores. Unbaited is best. They also don't seem to eat poison baits, which poses other potential issues for non-target animals.

Unbaited mouse traps, placed end-to-end, near active voles.

Cover the traps with a piece of gutter. Voles like the protection and shelter of above canopy, which is why they live under landscape fabric or in tall grass. They are less noticeable to predators.

Another tool that shows promise is using an organic fertilizer called Milorganite. This product has been around for decades and it's composted sewage sludge from the good people of Milwaukee, Wisconsin. (Don't worry--it's been heat-treated to 1600 degrees and poses no harm to humans.) Voles and other mammals, like rabbits, groundhogs, and even deer, don't like the smell.

Apply this fertilizer to any area of the landscape, including the lawn, landscape beds, or vegetable beds, at a rate of 15-20 pounds of product per 1,000 square feet. The 40 pound bag will cover about 2,000 square feet total and runs about $20. Now, this product is a repellent. It will make the voles go elsewhere, so using it in the entire landscape may not be practical, but focusing on active vole areas can work (or where you have rabbit damage). Once you apply the product, water it in. You'll notice the "earthy odor" for a day or so, but voles and rabbits will notice it for perhaps three weeks. Plan on applying it every month. It's not sold at most box stores, so check farm and ranch stores, or local hardware stores. As a side note, it's an excellent fertilizer, so you can use this to fertilize your lawn too.

Milorganite has been found to work to repel voles and rabbits in the landscape.

I should also point out that Extension doesn't usually list specific products, but Milorganite was tested in several research studies at the University of Nebraska, which is why we're recommending it. We'd love to hear if it works for you--be sure to let us know!

It's always something, isn't it? If it's not voles, it's late spring frosts. Or hail. Life as a gardener is truly a test of patience.