Germination pattern and inoculum transfer of entomopathogenic fungi and their role in disease resistance among Coptotermes formosanus (Isoptera: Rhinotermitidae)
2013
Hussain, A. (South China Agricultural Univ., Guangzhou (China). Dept. of Entomology) | Ming-Yi, T. (South China Agricultural Univ., Guangzhou (China). Dept. of Entomology)
Laboratory bioassays were designed on the strains of Metarhizium anisopliae and Beauveria bassiana to check the feasibility of using "trap and treat" method for controlling Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Different percentages of exposed C. formosanus workers 100%, 50%, 25% and 1% were then allowed to mingle with unexposed termites 0%, 50%, 75% and 99%, respectively. The mortality of combined group suggested that as the number of exposed individuals decreased, capacity of the workers to resist disease through mutual grooming was increased. Lower percentage of exposed individuals (1%), could not transfer inoculum resulting very low mortality (less than 3%) in any studied fungus. The strains of M. anisopliae were better than B. bassiana in producing epizootics in the experimental units because these strains produced more directly penetrating appressoria (62-67%), compared to B. bassiana (43-52%). These directly penetrating appressoria might be related to the virulence of the strains. We conclude that grooming ability to protect the termites from fungi is only workable when lower percentages of individuals are exposed. The workers may play pivotal role in the failure of disease epizootics by "trap and treat" method in the field through all grooming because a colony of C. formosanus comprised of millions of individuals and little inoculum can not be spread among the nest-mates, resulting failure of disease transmission in the field.
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