Judy, I have had success with keeping vole damage to a minimum by placing 14-2-2 Repellex tablets in and around the crown of susceptible plants. It is non-toxic, although not for use on edibles. It has not been very effective for deer or rabbits for me, although the manufacturer makes such claims. You can purchase these from the manufacturer in Canada or you might also find a reseller in the United States. See http://www.repellex.com/ Regards, Jay