Pythium species are a type of fungus that is the cause of "damping off" in seedlings, and bud and root rot in larger plants. First Report of Crown and Root Rot Caused by Pythium aphanidermatum on Industrial Hemp (Cannabis sativa) in Arizona. (USA) (full - 2021) https://apsjournals.apsnet.org/doi/10.1094/PDIS-01-21-0065-PDN During July and August 2020, symptoms of leaf yellowing and browning, sudden wilting, and death were observed on industrial hemp plants (Cannabis sativa L.) in several drip-irrigated fields in Yuma and Graham county, Arizona. About 85% of plants showed severe crown and root rot symptoms. A high percentage of affected plants collapsed under intensive heat stress. Shriveled stem tissue with necrotic lesions can often be seen at the base of the plant, extending upwards more than 5 cm. Internal tissue of main stem and branches was darkened or pinkish brown. Outer cortex of root bark was often completely rotten, exposing the white core. Cottony aerial mycelium was visible on the surface of stalk of some of the infected plants in two fields in Yuma. (snipped for length, plus it goes "all technical" on how they IDed the type of fungus) Granny