A new disease of orchids in Puerto Rico: Pythium black rot

Abstract

Reports of a black rot of orchids, (Laelio—Cattleya and Cattleya spp.) growing in greenhouses and outdoors in the Metropolitan Area, were received early in November 1949. The weather was chilly and humid during the month of November and December 1949, and through February and March 1950. The temperature during November and December varied from.a low of 16°C, during the night to a high of 26°C. during the day. At the end of February, 1950 temperatures from 20 to 24°C. at night, and 26 to 30°C. during the day were prevalent. The average relative humidity was around 90 percent most of the time because of frequent rains and foggy weather.