On Halicoverpa. armigera  in cotton, the fungus incidence was noticed from 43rd to 49^th standard week attaining peak in the 48th and 47th standard weeks during 1996 and 1997, respectively. In redgram, the fungal epizootics appeared in the 43rd  week, and reached peak in Die 48th standard week before disappearing from the ecosystem after 51st week during both 1996 and 1997. Fungal incidence ki Stylosanthes was delayed by three weeks in comparison to cotton and redgram. Its activity was noticed for short period of 6 weeks from 46th  to 51st  standard week during both the years 1996 and 1997, Peak incidence was recorded on the 48th and 49th standard week in 1996 and 1997, respectively. Among the three crops, Stylosanthes provided better habitat for the fungus with 12.90 per cent incidence followed by redgram (9.31 %) and least in cotton (5.9%). Correlation studies between disease incidence of N. rileyi on H. armigera in different crop ecosystems and weather parameters of the same and previous week during both the years failed to establish relationship between any of the variables recorded.