First report of Botrytis cinerea causing flower blight on macadamia in South Africa

Macadamia cultivation plays significant role in the economy of South Africa. Despite its importance, the industry grapples with disease-related challenges, notably flower blight, which threatens substantial economic losses by affecting yield and nut quality. In 2022, diagnostic services at the Agricultural Research Council and the Forestry and Agricultural Biotechnology Institute received macadamia flowers displaying blight symptoms. Employing two methods for fungal isolation, 25 isolates were obtained which were classified into one group based on morphological characteristics. DNA analysis identified the isolates as Botrytis cinerea. The pathogenicity testing was conducted on macadamia flowers to confirm Koch's postulates. This is the first report of B. cinerea affecting Macadamia integrifolia Maiden & Betche in South Africa, underlining its potential threat to the industry.