Title : First report of Neofusicoccum parvum causing stem canker of cannabis in South Africa
Abstract:
Hemp (Cannabis sativa L.) is a highly adaptable plant with a long history of cultivation, dating back to ancient civilizations such as those in China, Mesopotamia, and Egypt as early as 8000 BCE. Unlike marijuana, hemp contains only trace amounts of tetrahydrocannabinol (THC), the primary psychoactive compound found in marijuana. Hemp has a wide range of applications across multiple industries, including textiles, construction, food, and medicine. Widespread dieback of commercially planted cannabis in open field production, was observed in the 2024-2025 planting season in South Africa. Samples of diseased material were obtained from one farm in the Northwest Province and five farms in the Limpopo Province of South Africa. Symptoms included dieback and vascular discolouration of stems. Isolation from diseased material yielded cultures resembling Botryosphaeriaceae species. DNA sequencing and phylogenetic analyses of the tef-1α and tub2 gene regions identified the fungi as Neofusicoccum parvum. This species is a pathogen and endophyte of various native and plantation trees, as well as several horticultural crops, causing dieback and stem canker. It can be present as an endophyte in the plant, not causing any symptoms, until the plant is stressed, when disease expression will occur. Controlling the pathogen is difficult as it involves sanitation including cutting out diseased stems as well as limiting plant stress. It is therefore imperative to start with clean planting material and to ensure that mother plants used to make cuttings, are disease free, or to use certified disease-free seed. Monitoring of the disease will be continued in the next planting season to determine its impact on production.
