Jahrelanger Widerstand von amerikanischen Hemlockstannen gegen die Angriffe einheimischer Borkenkäfer

1953/1954

S. 209-217

Unselbständiges Werk

200170752

A stand of American Tsuga heterophylla, about 25 to 30 years old, was almost ruined by European fir bark beetles on a fresh Northern slope near Freiburg. The outbreak started perhaps in 1947 and was not finished yet in 1953. Damages were especially caused by Ips curvidens, spinidens and Vorontzowi. At the beginning of the outbreak plants were healty and their osmotical valus normal in regard to their location. For at least 3 years the beetles were kept off by large amounts of resin. But continuously they succeeded in boring egg galleries, thus weakening the trees in growing extent. After these egg galleries had appeared twics densely crowded on two to three meters in summer the strong resistance of the Tsuga broke down. Usually the 4. attack led to galleries with larcae, pupae and young adult beetles. For a success the bark beetles raised at least 4 generations in at least 3 years.