Technological development for the commercial production of viral insecticide
1990
Tipvadee Attathom | Sudawan Chaeyohomsri | Chalit Mahattana-art (Kasetsart Univ., Kamphaengsaen Campus, Nakorn Pathom (Thailand). Faculty of Agriculture. Dept. of Entomology)
Best biotype of bollworm for laboratory colonization was selected from wild populations collected from 11 different areas in Thailand. Bollworm population from Nakornsawan province exhibited the best growth performance in the laboratory and the highest potential rate of population increase. Several diets used for rearing the host larvae were compared and the mung bean diet was shown to be superior to the others. Technology for diet such as preparation, dispensing and handling of insect larvae on artificial diet were developed. Six strains of nuclear polyhedrosis virus of H. armigera were locally lsolated from infected insects and are being investigated for their molecular characteristics, pathogenicity, efficacy and relatedness. The virus was produced in third instar bollworm larvae, the most suitable larval stage for virus production. Virus recovery was accomplished by extraction the virus from infected bollworm, filtration and concentration. Bacterial contaminants found in harvested virus preparation included Bacillus brevis, B. subtitis, B. coagulans. B.pesteurii, Pseudomonas spp., Serratia mercesoens (Aicaiigenes faecalis) and Streptococcus spp. Numbers and types of the contaminants were lower in infected larvae freezed at -20 deg. Celsius prior processing. The storage stability of the virus was prolonged when kept at 0 deg. Celsius and 4 deg. Celsius as compared to at room temperature. Evaluation of the individual constituents of several adjuvants indicated that addition of corn oil, cottonseed flour, corn flour, sucrose, tween 20, yeast extract and protein hydrolyzate produced higher mortality in bollworm larvaes than did the virus suspension alone. Triton C6-7 surfactant had no effect on virus activity. The virus showed no pronounced effect on silkworm and honey bees.
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