EFFECTS OF TENDING MEASURES WITH SPRUCE ON THEIR NUTRITIONAL QUALITY FOR PHYTOPHAGOUS INSECTS

Investigations into the effects of tending measures with spruce (fertilising, de-branching, thinning) on their nutritional quality for the sawfly G. hercyniae indicate that both debranching and thinning exercise an influence. In contrast to the present doctrine the insects on the vigorous trees with good needle condition, long crowns and little root competition developed better than those on the poorly growing untreated control trees with small crowns and high root competition. Attention is called to the possible ecological significance for the low susceptibility of well-growing stands to forest pests.