Diagnosing systemic diseases.
Abstract A systemic disease is defined as one where a pathogen infects a plant systemically or affects the plant as a whole. There are certain types of diseases in hemp and cannabis crops that are viewed more as systemic rather than localized, based on both infection behaviour and symptom development. This chapter deals with diagnosing systemic diseases of cannabis crops, including vascular wilt caused by Fusarium Species, witches' broom caused by phytoplasmas, leaf curl caused by Beet curly top virus, plant stunting caused by Hop latent viroid, leaf chlorosis caused by Lettuce chlorosis virus and other viral diseases. Field diagnosis through symptom observation, problem classification, sampling, laboratory diagnosis by visual and microscopic examinations, isolation and colony observation, identification (PCR/DNA-based, morphological, ELISA), pathogenicity test, and key diagnostic evidence are described. Systemic disease management measures are discussed, focusing on inoculum prevention and vector control, monitoring mother plant health, managing insect vectors, controlling weeds, use of resistant varieties, avoiding contact transmission and reducing abiotic stresses.