Abstract: The occurrence of microsporidiosis ( Nosema sp. ) infecting Helicoverpa armigera was invest igated in the field. In 2000,Helicoverpa armigera occurred servious, and microsporidiosis showed epidemic trend in its populat ion.Theinfection rate of the 4th generat ion larvae was 49. 0%. After 2001, the infect ion rate decreased gradually. The microsporidian could infect H. armigera, Pieris rapae and Spodoptera exigua and couldn??t infect Lencania separata, Os??trinia furnacalis and Bombyx mori.The pathogenicity had strong to Helicoverpa armigera. The microporidian with the con??centrat ion of 10⁷ spores/ mL could control previous generation population and keep down next generat ion population. Themortality of the 2nd instar larvaewas 100% at 16 d after inoculation.The mortality of the 3rd instar larvae was 87. 8% at16 d after inoculat ion. When the microporidian with the concentrat ion of 105 and 10⁶ spores/ mL inoculated the 2nd instarslarvae, the eclosion rates were 32. 2% and 13. 3%, the mortalities of next generation larvae was 88. 9% and 100%. Themicroporidian was useful to control the next generation populat ion of H. armigera.

Key words: Helicoverpa armigera, Microsporidiosis, Occur in field, Pathogenicity

CLC Number: 

• S435.62