| Tick is a common ectoparasite of livestock and humans, which is responsible for transmission of various pathogens. Both the direct and indirect impacts of ticks are restraint of sustainable development of husbandry industry and menace human healthy. Currently, tick control is predominant by chemical acaricides, however, due to the issues of resistance and environmental security, the wide application of chemical acaricides has been limited. Therefore, biocontrol and immunization against ticks have become an urgent task and hot topic all over the world.In this study, Hyalomma anatolicum anatolicum and Rhipicephalus (Boophilus) microplus were the targets, and entomopathogenic fungi isolated from different areas in China were used to eliminate ticks and their effects were evaluated. Biological characteristics, synergistic effect with deltamethrin and optimized standard laboratory techniques for cultivation and fermentation of entomopathogenic fungi were evaluated by the numbers. Owing to the need to combat the shortage of lasting period of chemical acaricides and explore adaptive dispensarization for controlling ticks, we have obtained the biological parameters of ticks, which provide the basis of development for the new biological agents. The major achievements are as following:1. Twenty-nine entomopathogenic fungi were isolated from 84 soil samples and 24 bombysbatryticatus, and identified by morphology and molecular biology. As a result, 17 Beauveryia bassiana, 11 Metarrhizium anisopliae and 1 Paecilomyces lilacinus were obtained.2. Thirteen entomogenous fungi against engorged H. anatolicum anatolicum females were tested by immersing the ticks in conidial suspensions. Three strains with high spore output were selected for further study. These 3 Beauveryia bassiana had high virulence and were used against Rhipicephalus (Boophilus) microplus as well as engorged H. anatolicum anatolicum females in the different concentrations. After treatment, B. bassiana B.bAT17 showed higher virulence than other tested strains in terms of the pathogenicity against H. anatolicum anatolicum and Rhipicephalus (Boophilus) microplus.3. The impact of deltamethrin on the growth of mycelium and germination of spores of B. bassiana B.bAT17 indicated that deltamethrin inhibited its growth of mycelium and germination of spores. Inhibition was enhancing with the increasing concentration of deltamethrin. However, low concentration of deltamethrin showed good compatiblity with conidia of B. bassiana B.bAT17 strains. Synergistic effect with B. bassiana B.bAT17 and deltamethrin caused 100% mortality on all the ticks in all treated groups. Neither B. bassiana B.bAT17 nor deltamethrin alone at the same concentrations could cause the mortality as high as seen in the combinations.4. The factors studied were basic culture medium, temperature, pH, carbon sources, nitrogen sources, microelements and liquid fermentation medium. The results showed that B. bassiana B.bAT17 could grow well on PDA, PPDA, PDAY, SDAY and SMAY medium. Comparatively, B. bassiana B.bAT17 had the fastest growth on PDA and the highest spore yields on PDAY. Temperature was the major factor that affects on growth speed and yields of B. bassiana B.bAT17. It showed that 25°C was the optimal temperature for both hyphal growth and the sporulation. B. bassiana B.bAT17 could grow at pH 4?10 with the fastest growth in alkali condition, and produce optimal sporulation at pH 5?6. Based on all of fungal indexes, glucose and yeast were the best carbon and nitrogen sources. The best solid fermentation medium was wheat bran + indian meal + rice flour mixed with 3/4 SDAY containing suitable K~+ in proportion of 2:1. |
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