First occurrence of teak leaf rust caused by Olivea tectonae in Cote d'Ivoire and Africa.
In September 2017, leaf rust was observed on 28-year old teak (Tectona grandis) in the region of Haut Sassandra, Cote d'Ivoire. The disease was then recorded from another teak plantation on trees that were more than 20 years old, in the vicinity of the city of Gonaté. Some teak plants were severely infected. In both plantations disease prevalence was assessed using a "zigzag-monitoring approach" investigating approximately 540 teak trees and reached around 60%. Infected leaves initially had small, angular, brown to grey, necrotic areas on the upper leaf surfaces. As the disease progressed the lesions enlarged and coalesced to form large necrotic areas. The lesions corresponded to numerous subepidermally erumpent uredinia on the lower leaf surfaces. Rarely, uredinia were detected on the upper leaf surfaces. The causal pathogen was isolated and identified as Olivea tectonae based on morphological and pathogenicity analyses. This is thought to be the first report of leaf rust caused by O. tectonae on T. grandis in Cote d'Ivoire and Africa.