Microcyclus

Microcyclus is a genus name used in mycology to describe a group of fungi that cause leaf diseases on various host plants. The most cited species is Microcyclus ulei, traditionally recognized as a pathogen of Hevea brasiliensis (the rubber tree). Infected leaves develop circular to irregular lesions and may progress to defoliation under favorable environmental conditions.

Taxonomic placement of Microcyclus has been unstable as molecular methods reshape fungal classification. Some authorities have treated it as part of Ascomycota with uncertain familial assignment, while others have moved several species to related genera. As a result, the circumscription of Microcyclus varies across sources.

Biology is typical of plant-pathogenic fungi that produce spores on leaf surfaces; rain splash and wind aid dispersal. Infections are favored by warm, wet climates. Symptoms include light or dark brown lesions, chlorosis surrounding the spots, necrosis, and potential premature leaf drop.

Geographically, reports originate from tropical regions where rubber trees and other hosts are grown. The disease can spread via infected planting material, tools, and infested plant debris.

Management emphasizes preventive measures and cultural control when possible, including use of resistant cultivars, pruning to improve air circulation, reducing leaf wetness, timely fungicide applications, and quarantine to minimize introduction of inoculum.