Common methods for mole control are baiting with earthworms impregnated with thallium sulphate or strychnine, gassing with pellets developing phosphine, and trapping. Seasonal cycles in burrowing activity make it difficult to evaluate results of expensive control campaigns and may give a false impression of efficiency.

The second-generation anticoagulants. difenacoum, bromadiolone, and brodifacoum have taken over a considerable part of the rodenticidal market during the last six to eight years. This is partly due to the higher efficiency against a larger spectrum of rodent pest species and partly to the increasing problem of physiological resistance to the older anticoagulants. Resistance of practical importance has, however, now been encountered to difenacoum and bromadiolone in Europe, i.e., UK and Scandinavia. Brodifacoum, in spite of the evidence of a somewhat increased tolerance in some commensal rodent populations, still must be considered a highly effective rodenticide against almost all important rodent pest species. Research leading to the synthesis of similar potent anticoagulant molecules or other slow-acting rodenticides should be encouraged in order to cope with the possible development of resistance also to brodifacoum in the future.

Four Microtine species, the field vole (Microtus agrestis), the continental vole (Microtus arvalis), the water vole (Arvicola terrestris) and 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.

Flocoumafen is a new anticoagulant rodenticide with an acute toxicity between that of bromadiolone and brodifacoum. It has performed well in field tests against house mice and susceptible as well as resistant brown rat populations. Danish lab tests reveal a considerable variation in susceptibility between rodent species and indicate that practical problems in the control of certain Scandinavian bromadiolone-resistant house mouse populations may arise shortly after introduction.