Studies on the Relation between Fungi and Insects

(II) On the Pathogenicity of Muscardines and their Growth in the Insect-blood (1)

Abstract

1) The pathogenic activity of white, red and yellow muscardine (Beauveria Bassiana VUILL., Isaria fumosorosea WIZE and Isaria farinosa FR. respectively) is most vigorous to the host insects on which they are most abundantly found, namely to domesticated silkworm (Bombyx mori L.), Kyoso-fly-pupa (Sturmia sericariae C.) and pyralid moth (Margaronia pyroalis W.) respectively.
2) White muscardine is more pathogenic to domesticated silkworm than to the wild silkworm (Theophila mandarina MOORE). The pathogenicity of this fungus is also influenced by the races of silkworm.
3) Although white muscardine is invariably pathogenic to domesticated silkworm regardless of the larval stage, the pathogenicity of green muscardine is conspicuously affected by the stage, being vigorous to the silkworm in earlier stage and faint to the one in late stage. The incubation period of green muscardine is longer than the one of white muscardine. The reason why green muscardine occurs simultaneously in the third moult was discussed.
4) The pathogenicity of white, red and yellow muscardines to silkworm, Kyoso-flp-pupa and pylarid moth respectively and the one of green muscardine to the various stages of domesticated silkworm were found to be directly proportional to the germinating rate of spores, the growth rate of germ-tube and the speed of cylindrical-spore-formation of the causal fungi in the insect's blood.