This is the time of year (October – April) when voles are extremely active in the garden, as you can see below from this recently chewed aspidistra in the garden. Voles are vegetarian mouse relatives that tunnel underground eating the roots of plants…usually those with the most expensive price tags. Once the roots are gone, plant remains are then stealthily pulled underground so you won’t notice the damage.
The formulation of most commercial vole baits changed in the last few years and are now composed of Vitamin D (Cholecalciferol). While Vitamin D is quite effective on voles, it still needs to be kept away from pets, since too much Vitamin D isn’t a good thing. We prefer the large blocks, compared to the smaller pellets since they are less likely to be swallowed by pets.
We’ve also always recommended using PVC-tubes for vole feeding, or simply bury the bait underground or under a rock, etc. Of course, there’s always the option of using mouse traps to catch voles, which is much more labor intensive and not really really viable on a large scale.
Vole bate stations should be placed every 10′ apart in high problem areas, and must be checked every couple of weeks to make sure bait remains. We have been using various vole baits for 35 years, and have yet to have any issues with our fleet of garden cats, but it is important that you be careful with bait placement.
Once vole populations are under control, we recommend using traps around the edge of your property to prevent new intrustions. We do this by spreading a square of black plastic with bait underneath, along your property line…every 50′ or so seems to be adequate. The voles are attracted to the black plastic and the bait, so this way there never venture further into the garden.