Despite of more than two decades of intensive forest-decline research the reasons for the very high damage-levels especially of broad-leafed trees are not completely understood. In former investigations only very few groups studied a possible correlation between the usage of high-tonnage pesticides in modern agriculture and the observed damages of trees. Evans et al. have observed in greenhouse experiments a correlation between chlorophyll production of beech leafes and pesticide contamination (Evans et al., 1994). The symbiosis of a number of fungis with the roots of the tree (mycorrhiza) is observed for most of all higher plants. Concerning some useful plants like legumes this symbiosis is well known to be sensitive to pesticides (Abd-Alla et al., 2000). However, this sensitive area of the ecosystem beech-forest has never been investigated before regarding pesticide input. Very first results of experiments to determine pesticide-fluxes in beech-forest are presented including the question whether forests may act as a sink for pesticides and dicussing the fate of pesticides in beech-forests.