Biological studies of Hirsutella thompsonii, a fungal pathogen of phytophagous mites in Thailand
1996
Yupa Phung-Noi
Survey of phytophagous mites and their parasites on various host plants were made. Twenty seven isolates from eriophyid and spider mites cadavers were identified into Aspergillus, Fusarium, Hirsutella, Paecilomyces, Penicillium and Verticillium. Only 4 isolates were screened on their vilulence on mites. Hirsutella sp. H1 were the most vilulence and induced upto 80 percent pathogenicity when the spore suspension of 1*10*[6)-1*10*[8) spore/ml were applied onto the adult citrus rust mite. Isolates H2, H3 and H4 caused only 14-36 percent pathogenicity when inoculated with spore suspension of 10*[6) spore/ml. Pathogenicity increased gradually with increasing in concentration, however, all 4 isolates showed no significant different in pathogenicity at the concentration of 10*[8) spore/ml. Culture broths filtrated of those 4 isolated did not effect mite's mortality. Growth of 4 isolates on 4 kinds of solid media (MEA, SYA, CDA and PDA) at 15, 20, 25, 30 and 35 deg C were made. SYA is the most appropriate media for all followed by PDA MEA and CDA respectively. All isolates grew well at 25-30 deg C whereas tiny growth was observed at 35 deg C. The same result were obtained when cultured in liquid media at 25 deg C. Fungi grew well in SYB and then PDB, CDB and MEB respectively. Effect of various level of pH 4, 5, 6, 7, and 8 on growth of fungi in SYB at 25 deg C showed that pH 6 was the most suitable one. Presumably, all 4 isolates favored acid more than alkaline media. parasitism and toxicity of 4 fungal isolates on fruit fly, bee and silk worm were studied. No parasitism association and toxicity effect of fungi on other insect except that the 2nd instar silk worm refused to feed on mulburry leaf spray with culture filtrate.
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