Vole Control in Blueberry Fields
Video 1: Vole Identification and Damage
This video points out the distinguishing features of the different species found in blueberry fields and how to identify fresh vole tunnels and runways. It illustrates the difference between root damage caused by voles: two parallel teeth marks from their incisors, versus weevils which only leave a single grove around the root system. Voles are most abundant in the fall and early winter when the young disperse, and damage typically occurs in the winter when there is a lack of herbaceous plants for the voles to eat.
Video 2: Minimizing Vole Damage
This video presents BMPs options for how you can reduce vole damage in berry fields using an IPM approach. Monitoring is a key component of any IPM approach, so it is important to conduct monthly surveys for evidence of voles such as fresh vole tunnels and runways and associated damage. This will help identify potential problem areas in your field. Reducing vole abundance can be achieved through vegetation management; keeping grass short or cultivating between the berry rows to remove the vegetation. Vegetation management should also be done around the perimeter of the field. Another option is to encourage vole eating raptors to hunt or nest in your field, this can be achieved by installing perches or barn owl and kestrel nest boxes. However, if you are encouraging raptors it is important to not apply rodenticides in the field as this can lead to secondary rodenticide poisoning of raptors.
Video 3: Using Rodenticide
If vole damage persists after persistent vegetation management, then applying rodenticides is your last resort to control voles. This video takes you through the steps on how to safely and efficiently apply rodenticides in your berry field. The first step is to choose your product. In Canada, only products containing the active ingredient diphacinone, chlorophacinone or zinc phosphide are allowed to be used in berry fields. However, it is important to note that zinc phosphide does not work well in the wet climate we have on the South coast as it dissolves and becomes phosphine gas when wet. Identifying the problem area is the next step, voles have small territories (~1m2) so rodenticides should only be applied to areas where rodent damage is occurring. Bait should be placed in a tamper resistant securely fastened bait station. Typically, in berry fields, t-bait stations strapped or wired to a post or the berry bush are used. After rodenticides are applied, it is important to monitor the area every second day to check for recent vole activity, remove vole carcasses, and if needed refill bait stations and ensure all bait stations are securely fastened. After damage has subsided and there are no fresh signs of vole activity remove the bait but keep up the monitoring to ensure that there is no new damage. Removing bait reduces the risk of non-target species consuming the bait such as other small mammals, insects and song birds. It also reduces the risk of voles becoming resistant to rodenticides. If rodenticides are applied to a field do not attracts raptors to hunt in this field due to risk of secondary rodenticide poisoning.