The intensification of agricultural production in the Mekong Delta has faced serious challenges with respect to increased use of agrochemicals and especially pesticides. The indiscriminate use of pesticide could potentially impact on the long-term food production, environmental and human health in the delta. The aim of this thesis was to investigate the negative side effects of the current use of pesticides on climbing perch (Anabas testudineus) in rice fields using brain acetylcholinesterase (hereafter referred to as AChE) activity as a biomarker. The empirical work, on which this thesis is based, includes structured questionnaires, laboratory and field experiments. First, a field survey using questionnaires was carried out to gain a better understanding of the current state of rice farming systems, the use of pesticides and attitude to pest management strategies among rice and rice-fish farmers, as well as to provide basic information for the set-up of the laboratory and field experiments. Secondly, laboratory studies were conducted to clarify if the selected insecticides applied alone and in mixtures caused negative side effects on climbing perch fingerlings. Thirdly, further toxicity studies were carried out, under rice field conditions, to further investigate the toxicity effects of the insecticides, applied alone, in mixtures and under sequential applications, on climbing perch fingerlings. The results showed that although there were a more selective use of pesticides and an increased awareness among farmers of the negative side effects of pesticides in 2007 as compared to 1999, the current use of pesticide in the Mekong Delta still cause many problems to the environment and human health. Chlorpyrifos ethyl (hereafter referred to as CPF) was found to cause a significant and more prolonged inhibition on the brain AChE activity in climbing perch than fenobucarb (hereafter referred to as F). The inhibition by the mixture of CPF and F were significantly higher than the inhibition by only F, but less prolonged and significant lower than the inhibition by only CPF. The results suggest that the combined effect from a mixture of F and CPF can create both additive effects initially and later antagonistic effects. CPF and F applied at concentrations used by farmers, either as separate doses, in a mixture or in sequential doses, decreased the brain AChE activity, growth and survival rates in climbing perch. The results demonstrate that brain AChE activity in climbing perch is a relevant biomarker for monitoring of exposure to, and sub-lethal impacts from organophosphates and carbamates under tropical conditions. The result also shows that 2-PAM re-activate the brain AChE activity, and can be used as an alternative method to assess the AChE inhibition level in organisms recently exposed to OP’s, in situation where it may be difficult to find unexposed individuals as controls. In conclusion, this thesis shows that the current use of pesticides in the Mekong Delta has a negative effect on climbing perch living in rice fields. It indicates that a sustained long-term food production in the Mekong Delta must be based on ecological principles, taking advantages of ecosystem biodiversity and productivity, and not through intensified use of pesticides. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Submitted.</p>

My thesis is devoted to the resistance of pollen beetle (Meligethes aeneus, son. Brassicogethes aeneus Fabricius, 1775) to pesticides in selected localities in southern Moravia. Collecting adults was performed in the spring of 2013 by tapped into polyethylene bags. Adults are collected from the stands of oilseed rape, mustard and poppy. Tests were performed on the basis of the methodology of Insecticide Resistance Action Committee number 011, 021, 025. In total, we tested the pollen population from 18 locations. For testing, we used the following chemical substances: Biscaya 240 OD, cypermethrin, lambda-cyhalothrin, tau-fluvalinate, etofenprox, chlorpyrifos(ethyl). We evaluated 100% of the registered dose of pesticides after 24 hours. From the results of the individual populations, we found large differences in resistance to chemicals.

This thesis was compiled during the solution of the project MA NAZV QJ1230077 and it is focuses on monitoring of pollen beetle (Brassicogethes aeneus, Fab., 1775) populations resistence to selected insecticides, in particular lambda-cyhalotrin, cypermetrin, tau-fluvalinate, Biscaya 240 OD and chlorpyrifos-ethyl in South Moravia. Beetles were collected during the spring 2016. Their sensitivity to these insecticides active ingredients was tested in laboratory. Various concentrations of active substances and beetles´ mortality after 24 hours was evaluated according to methodology IRAC (adult-vial-test met. 11, 21, 25, www.irac-online.org). Beetles´ sensitivity depends on the dose of the active substance and the location where the beetles were taken from.