Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of southern blight caused by Sclerotium rolfsii in industrial hemp in Southern Virginia.

Abstract

Since legalization of industrial hemp (Cannabis sativa) in Virginia, USA, an increasing number of farmers are planting hemp in order to supply the rapidly expanding industry. In late July, a hemp field located in Mecklenburg County in southern Virginia showed wilting symptoms similar to southern blight. Approximately 10% of the field had patches of diseased plants. They were grown under plastic with drip irrigation and consisted of high-cannabidiol (CBD) hemp cultivar Cherry Wine. The infected plants showed light brown stems near the base, which were covered with extensive cottony white mycelia. The crowns and lower stems of the plants and the surrounding soil had numerous brown to dark brown sclerotia (diameter of 1-1.5 mm). Initially, plants showed yellow leaves, and as the disease progressed the entire foliage turned dark brown and permanently wilted. The causal pathogen was isolated and identified as Sclerotium rolfsii [Athelia rolfsii] based on morphological characteristics, sequence analysis of the internal transcribed spacer (ITS) region and pathogenicity test. This is thought to be the first report of southern blight caused by S. rolfsii in hemp in southern Virginia. High summer temperature and overirrigation most likely were conducive for this disease.