Effects of herbicides on target and nontarget organisms

Abstract

Pesticides have significant environmental and public health impact. This study examined the target and nontarget effects of herbicide Sekator OD 375 (amidosulfuron and iodosulfuron) to target weed species Chenopodium album L., to two nontarget plant species – barley Hordeum vulgare L.; duckweed Lemna minor L. and one aquatic micro-invertebrates Daphnia magna. The terrestrial plants were sprayed directly with various dilutions of herbicide sprays (solutions equivalent to 0.1-0.001 of recommended field application rate), the aquatic plants and micro-invertebrates were affected by the same concentrations of herbicide in their growth medium. The measured endpoints in plants bioassays were: survival, height of the shoots, the dry biomass, concentrations of malondialdehydes (MDA) the growth rate of L. minor. The mortality of D.magna was observed. All plant species had a strong phytotoxic response to herbicide application, though the response of target species was more pronounced. The growth of shoots of Chenopodium album and Hordeum vulgare was inhibited by 37.1% and by 18.4% respectively. The dry biomass of barley was by 33 %, of Chenopodium album – by 71,5% lower than in control. Lemna minor showed extremely strong response: in the highest concentrations of herbicide the breakdown of all colonies was observed. The biomass of Lemna minor in lowest concentrations of herbicide was approximately by 31 % lower than in control. Application of herbicide provoked an oxidative stress, the concentrations of MDA in Ch. album and H. vulgare were, respectively, by 8.4, and 1.2-fold higher than in control. The micro-invertebrates were very sensitive and application of herbicide caused 50-100 % mortality of micro-invertebrates. The study revealed that application of herbicides causes the adverse effects not only in target vegetation, but in nontarget organisms as well.