The pathogen Oidium euonymi-japonici (anamorph) causing powdery mildew of Euonymus japonicus in Kashmir valley overwintered asexually as mycelium on intact infected twigs which started producing conidia in the 4th week of February and continued till ending October during both the years of study 2013 and 2014. The pathogen ceased to produce conidia from the 1st week of November to 3rd week of February, 2013–2014 and 2014–2015. On intact-overwintered infected twigs, maximum conidial production and viability was observed during 1st week of April and 1st week of August in both the years. However, no conidial formation was observed on the twigs, kept 10 cm deep in the soil. The cross inoculation study revealed that inoculum from Euonymus japonicus successfully infected all the other Euonymus genotypes tested but failed to infect the weeds and other test hosts and vice versa.