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Four Microtine species, the field vole (Microtus agrestis), the continental vole (Microtus arvalis), the water vole (Arvicola terrestris) arid the bank vole (Clethrionomys glareolus) are the most harmful rodents in forests, fields, orchards and gardens in Northern and Central Europe. Except for the latter they are all herbivorous, their food consisting to a very low degree of seeds and grain. As a consequence dry poison baits are not well accepted most of the year. The only economic and effective control method until now has been surface spraying with the chlorinated hydrocarbons endrin and toxaphene. As these chemicals are now black-listed in many European countries, and their use severely restricted in other countries, no effective means for controlling these rodents exist for the time being. New surface sprays without the persistence of endrin, but with a more long-lasting effect than parathion, are severely needed if the extensive damage to trees and crops shall be reduced.