THE BREEDING OF HARD PINE TYPES RESISTANT TO THE EUROPEAN PINE SHOOT MOTH (Rhyacionia buoliana Schiff.)

The susceptibility of hard pines of the Lariciones group to infestation by the European pine shoot moth is postulated by Neugebauer to depend on the amount of resin flow the attacked pines can produce. Abundant resin flow tends to drown out the insect and makes the pines resistant. Warm and moist summers enhance abundant resin flow, cool dry summers retard it. Inherent differences in susceptibility are found between pine species and are suspected at a subspecific level. Variation in degree of infestation is conditioned by possible inherent differences in susceptibility and by the degree of matching of the planting site to the requirements of the materials in respect to summer climate. Breeding possibilities utilizing the resistance found in Japanese black pine and in the Austrian pine group are discussed in relation to the production of improved types of red pine and Scots pine. The possible uses of Japanese red pine and other species as intermediates in such a breeding project are mentioned. The inclusion of breeding for resistance to shoot moth in a general breeding program of hard pines is considered desirable.