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Rodents and hares are very harmful pests in forest plantations in the Holarctic zone. No effective way to control damages by these pests is known. There is large variation in resistance of different birch species, origins and families. The resistance does not seem to be correlated to growth of seedlings, thus the prospects for resistance breeding are considered good. There seem to be large variation even within birch families which can partly be explained by morphological differences between seedlings. Also the nursery treatment seems to determine the palatability of seedlings to herbivores. Ways to produce resistant genotypes for the use of practical forestry are discussed.