Abstract
In this study, side-effects of various pesticides on collembolan species covering different life forms (Isotoma anglicana, Lepidocyrtus violaceus, Folsomia fimetaria, Heteromurus nitidus and Onychiurus armatus) were examined in laboratory and field experiments. The principal aim of the study was to develop choice experiments with Collembola for the quantitative assessment of avoidance behaviour. Avoidance can potentially lead to population declines due to inhibited immigration or escape from contaminated areas. One herbicide (Betanal, active ingredient phenmedipham) and five insecticides were tested. These included two synthetic pyrethroids (Karate, a. i. lambda-cyhalothrin and Cymbush, a. i. cypermethrin), two carbamates (Croneton, a. i. ethiofencarb and Curaterr, a. i. carbofuran) and the neem seed-kernel extract formulation NeemAzal T/S (active ingredient azadirachtin A). To determine the influence of the six pesticides on springtail mortality and mobility, acute toxicity tests over 24 hours and seven days were carried out. All pesticides except NeemAzal T/S caused inactivation of the springtails after 24 hours. Whereas the acute toxicity of Karate, Croneton, Curaterr and NeemAzal T/S could be attributed to the active ingredients, these were non-toxic in the case of Betanal and Cymbush. It is concluded that the formulations of Betanal and Cymbush contain toxic adjuvants. Effects on reproduction were assessed with F. candida. Cymbush had no adverse effect on reproduction after 28 days. All other pesticides affected reproduction with EC50-values below those of acute toxicity. Repellency could be stated for all six pesticides by means of choice experiments. For Betanal, Karate and Cymbush the endpoint avoidance behaviour proved to be more sensitive than reproduction. By means of the choice test behavioural reactions can be detected that could lead to an emigration of springtails out of contaminated areas and thereby affect the community structure of the biocoenosis and soil fertility. Furthermore, it provides additional, ecologically important information about side effects of pesticides on non-target organisms. Avoidance induced by vapours of the test substances was quantified using an innovative design for testing collembolan olfaction, in which O. armatus was able to detect Betanal, Croneton, Curaterr and NeemAzal T/S without direct contact. Finally, the results of the choice experiments with Betanal and Cymbush were compared with investigations in the field. For this purpose, the colonization of Betanal- and Cymbush-contaminated litterbags and -boxes by springtails was investigated. The experiments showed no significant differences between the colonization of contaminated areas and controls. |
