Wirkung von Larvenkot von Dendrolimus pini L. (Lep., Lasiocampidae)nach Fraß an Kiefer auf Keimung und Keimlingswachstum von Kiefern‐, Birken‐und Eichensaat

Germination and growth of Pinus sylvestris L., Betula pendula Roth. and Quercus robur L. were investigated under laboratory conditions. Sterilized sand was used as the substrate and supplied with (a) increasing amounts of faeces of larvae of Dendrolimus pini L. which had been reared previously on Scotch pine and (b) a solution of NH 4 NO 3 of the same N‐concentration as the faeces. The germination of pine and birch decreased strongly with increasing amounts of faeces, whereas the germination of oak was unaffected. When the inhibition of germination was overcome the further growth proceeded according to the species‐specific growth pattern during a period of 200 days (oak) and 300 days, respectively (pine, birch). It was influenced neither by the supply of faeces nor of fertilizer. It is concluded from the results that the faeces of phytophagous insects contain inhibitory components which become effective only during the germination process of the species if there is a poor supply of nutrients in the seed (pine, birch). The subsequent stage of germ growth however, is not affected. The results are discussed in terms of a possible ecological function for insects as regulators of the species composition following mass propagations.