Effects of various tending measures on the nutritional quality of Norway spruce for phytophagous insects.
Studies were made in Germany on the effects of fertilizer application, pruning and thinning of Norway spruce [Picea abies] on the quality of its foliage as food for the sawfly Gilpinia hercyniae. Both pruning and thinning had an effect on foliage quality. Sawflies developed better on vigorous trees with good needles, long crowns and little root competition than on untreated control trees with poor growth, small crowns and strong root competition. The possible ecological significance of this finding is briefly discussed.