Comment:
Hemp powdery mildew is primarily caused by the obligate biotrophic ascomycete fungi Golovinomyces ambrosiae (G. ambrosiae). However, there have been reports of Podosphaera macularis (P. macularis), the causal agent of hop powdery mildew, infecting hemp plants in various locations across the U.S. and Canada. Powdery mildew is an easily recognizable, airborne and polycyclic disease. It initially appears as white, typically round patches on the adaxial leaf surface. These patches expand and eventually coalesce, causing defoliation in the most susceptible genotypes. The disease can affect leaves, stems, and floral tissues, resulting in a reduction in quality of high-cannabinoid market products. The infection is favored by high humidity, although free-standing water on the leaves will delay its progression.