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Garden Help Desk: Voles or grubs might explain potato damage

By USU Extension - Special to the Daily Herald | Jan 11, 2025
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The damage in this potato has distinct margins, suggesting pest damage.
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It is easy to spot this vole trail coming from a perennial bed that is adjacent to a lawn. Voles will clip back the grass to create easy access and movement.
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White grubs are root feeders. They range in size from very small to over 1 inch in size, depending on the species. They are typically C-shaped when exposed. Handpick any that you see.
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When potato tubers show older damage at the time of harvest, it's a strong clue that damage happened during the growing season, not from mechanical damage during harvest.
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Vole trails in residential landscapes may be seen coming from sheltered sites that are adjacent to lawns. This rock retaining wall is a good example.

Can you tell me what caused these holes in potatoes? They weren’t rotten but looked and felt like something had eaten them. This is how they came out of the ground.

Voles may be the pest that helped themselves to your potatoes in the fall. Voles are small, sturdy-looking rodents. Larger than mice, their tails are shorter and their ears are smaller. It’s more common to see vole damage than to see the voles; they don’t like to be out in the open and spend most of their time in burrows or other sheltered locations. Another possibility is one of the white grub species we see here. Start by checking for vole activity first.

One easy place to check for vole activity is near shrub or flower beds. Voles don’t like to be out in the open, so they often shelter there where they have quick access to some protective cover from predators. Voles also leave trails in lawns. These trails often begin at the edges of lawns, landscape beds, rock retaining walls, etc. I’ve included a photo this week that show what the damage often looks like. If you have snow cover in your landscape, you may need to investigate a little further.

Making your yard less hospitable for the voles is the first control method you should try. Prune up low-lying shrubbery and keep leaf litter, clutter and debris raked out or cleaned up. Next year, mow your lawn regularly and keep flower and shrub beds weeded. Your goal is to reduce sheltered sites for the voles and increase opportunities for predators like cats, dogs and large birds.

If you garden in raised beds, you can try underlaying the beds with hardware cloth (remember, voles are small) but voles can easily scramble up into a low raised bed. Keeping a 2- to 3-foot-wide area around your raised beds vegetation-free may make voles more vulnerable to predation and discourage them, too.

When we talk about white grubs, we’re usually thinking about the ones that damage our lawns, but there are other beetle larvae that are sometimes found in garden soil, compost piles, etc. Most of these are harmless, but there can be plant damage if their populations are high enough. If white grubs are the problem, you should have found some in the soil in the area where the potatoes were growing, possibly a bit deeper in the soil than the potatoes you harvested. Grubs aren’t active right now, but they will become active in the early spring, pupate and emerge as adults to lay more eggs in late spring to early summer.

For your vegetable garden, light tillage combined with hand removal is a first step in control for grubs. As soon as the soil is workable this spring you can try checking for grubs and removing any that you find. Light tillage will also expose any grubs to birds and other predators as well as other environmental conditions. There aren’t many chemical controls that could be used in a vegetable garden and soil temperatures are too low in the winter for chemical applications anyway. Turning the soil to expose grubs to the elements and predators can be effective.