Study On Safety Assessment Methods And Effects Of Typical Microbial Pesticides On Fish

Microbial pesticide is a microorganism (e.g., a bacterium, fungus, virus or protozoan) as active ingredient, which can control crop diseases, pest, weed and rodent or promote crop growth. The annual production value of microbial pesticide has exceeded18billion US dollars. Bacillus thuringiersis (Bt), Beauveria bassiana (Bb) and Helicoverpa armigera nucleopolyhedrovirus (HaNPV) are important microbial pesticides.Because microbial pesticides are more environment-friendly products compared with chemical pesticides, the amount and scope of microbial pesticides are increaseing. However, more and more researches showed that some of microbial pesticides are adverse to aquatic organisms. In order to control application risk of microbial pesticides, some developed countries, including America, Canada and Japan, already have set up microbial pesticides test guidelines and technical specifications for safety assessment on fish. At present, there is no safety assessment guideline on effect of microbial pesticide on fish in China. This paper preliminary established safety assessment methods of microbial pesticide, and also tested the impact of three typical microbial pesticides on fish. The major research contents and conclusions are as follows:1. Establish the assessment methods of effect of microbial pesticide on fish.In this paper, we carried out route of exposure, environmental conditions of exposure, histopathologic change, growth and decline evaluation, infections of microorganism, and biomarker of sublethal doses of microorganism in safety assessment of positive strain (Aeromonas hydrophila) on zebra fish and crucian carp. The results showed that it was more easily lead to death of fish when microorganism exposure by way of injection and immersion in bacterial suspension after tail cut and dermis scratch at the optimum temperature for the growth of microorganism; Sensitive biomarkers in tests of sublethal doses of microorganism on fish are fish length, Superoxide Dismutaseon (SOD), trypsin, alkaline phosphate (AKP), glutamic oxalocetie transaminase (AST/GOT), alanine aminotransferase (ALT/GPT); Safety assessment of microbial pesticide includes level of lethal, the proliferate capacity of microbial pesticide, infections of microorganism, and biological effects of fish exposure to sublethal doses of microorganism.2. Test the toxicity effects of three typical microbial pesticides on fish.In this paper, we conducted toxicity effects of Bt, Bb, HaNPV on fish by the methods established. The results showed that Bt has infection toxicity, propagation toxicity and lethal toxicity on fish, LD50-7d of Bt for zebra fish and crucian carp were2.73×106cfu and3.38×107cfu at30℃. For zebra fish, Bt can induce pathological changes on the liver, kidney, and intestine. For crucian carp, the activity of SOD would increase, and trypsin, AST/GOT would decrease when exposured to sublethal doses of Bt; Bb has lethal toxicity on fish, LD50-7d of Bb for zebra fish and crucian carp by injection were5.51×105cell and2.24×107cell at26℃, For zebra fish, Bb can induce pathological changes on the gills, liver, kidney, spleen, and intestine. For crucian carp, the activity of trypsin, AKP, and ALT/GPT would increase when exposured to sublethal doses of Bb; HaNPV is safe to fish.