P.boehmeriae was first isolated in 1927 from the leaves of chinees silk tree in Taiwan. P.arecae is classified in group II.Sporangia are papillate and spherical, ovoid, ellipsoidal or obturbinate. Chamidospores are produced infrquently. P.boehmeriae is homothalic and oospores form abundantly in host tissues. Antheridia are amphigynous and almost spherical in shape often with a residual oil globule.Oogonia are smooth walledand hyaline to yellow. Optimum growth temperature is 25 degree Celsius