Conidiobolus coronatus is a major opportunistic insect pathogen belongs to order Entomophthorales which is distributed worldwide. Effect of C. coronatus against nymphs of Ricania simulans (Walker) (Recaniidae: Hemiptera) was studied under laboratory and field conditions. In laboratory, three isolates (Cc 1, Cc2 and Cc3) of C. coronatus were assessed against nymphs of R. simulans, at a single dose (1x10(7) conidia mL(-1)) on tea leaflets. Mortality percentage after a six-day period reached 100% and the median lethal time (LT50) values ranged from 3.19 to 3.66 days. In a field, C. coronatus strain Cc3 was assessed against nymphs of this pest, at a single dose (1x10(7) conidia mL(-1)) on apple plants. The LT50 values for nymphs were 4.33 days. Obtained findings suggest that C. coronatus strain Cc3 is a potent entomopathogenic agent that could be included against R. simulans in IPM programs.