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Integrovaná ochrana proti škůdcům a chorobám v akvaponii
FOLORUNSO, Ewumi Azeez Olatunji
This thesis has laid an essential foundation for developing aquaponics-safe approaches to address pest and disease outbreaks in aquaponics. Our review on adopting integrated pest and disease management in aquaponics not only customized pyramid-flow IPDMs for aquaponics but also inclusively initiated essential fish management pathways for aquaponics farmers who are primarily not fish farm experts. Furthermore, our review identified pathogen infestation challenges as priorities over macro-pests and diseases in fish culture units and the urgent need to establish safe phytopathogen management options. These conclusions were followed up by investigating safe biological control agents, where the efficacy of entomopathogenic and mycoparasitic fungi was investigated against powdery mildew, and their low-survival chance in RAS water was determined to affirm their suitability for different aquaponics designs (coupled and decoupled). With raving questions on the reliability of biological control, we explored potentially safe chemical control options that could be adopted for aquaponics systems, and investigated their possible negative impacts on aquaponics. The natural (azadirachtin, lecithin, and clove oi), microbial (spinosad) and synthetic (tebuconazole) pesticides investigated, runoff into nutrient solutions after foliar application, and were detected in significant concentrations at different time points post applications. Their percentage runoff in regard to spray solution varies significantly (0.1-2.3 %), owing to differences in the proportion of the active ingredients, recommended dosages and the properties of the compound. The percentage runoff of azadirachtin, eugenol, spinosad and tebuconazole ranged between 0.1 and 0.8 % of the sprayed active ingredients. On the other hand, 2.3 % of the sprayed lecithin were detected in the aquaponics water. Since eugenol and spinosad were detected at concentrations lower than their corresponding NOEC and LC50, they are considered safe for all aquaponics systems. Pyrethrum, on the other hand, was not detected in the nutrient solution, which could be due to its non-persistence and fast degradation in water. However, its active ingredient (pyrethrin) is highly toxic to fish and other aquatic organisms, and its usage should only be limited to decoupled aquaponics systems. Regarding their effects on fish and biofilter, tebuconazole had a significantly persistent effects on fish hematology, biochemical and antioxidative activities over a 28 day semi-static period, indicating its unsuitability for coupled aquaponics designs. However, tebuconazole did not have significant effects on nitrification processes in the biofilter at the maximum runoff concentration. Lecithin, on the other hand, altered and spiked ammonium and nitrite levels in biofilter at its maximum runoff concentration, making the compound unsuitable for coupled aquaponics. In contrast, only mild non-significant effects of azadirachtin and eugenol were seen in biofilter nitrification, fish hematology, and biochemical parameters, indicating their low risks for all aquaponics systems (when applied according to the manufacturer's instruction). Lastly, we explored the influence of biological control and fungicides on running aquaponics systems. T. virens, I. fumosorosea and L. attenuatum, controlled and suppressed powdery mildew over a period of four weeks. In addition, T. virens was able to improve the growth of the plant. The fungicides (clove oil, lecithin, and tebuconazole), on the other hand, did not show any influence on the basil growth.
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