Natural Occurrence of Microsphaera pulchra and Phyllactinia guttata on Two Cornus Species

Area of Science:

• Plant Pathology
• Mycology
• Horticultural Science

Background:

• Powdery mildew has emerged as a significant foliar disease affecting dogwood species, particularly Cornus florida, in the eastern United States.
• Previous observations indicated the presence of powdery mildew on dogwood leaves, necessitating a detailed etiological investigation.

Purpose of the Study:

• To accurately identify the powdery mildew fungi infecting Cornus florida and Cornus amomum.
• To differentiate between the two identified species, Microsphaera pulchra and Phyllactinia guttata, based on morphological and host interaction characteristics.

Main Methods:

• Field surveys were conducted to observe and collect infected dogwood leaves from C. florida and C. amomum.
• Ascocarp morphology and distribution of Microsphaera pulchra and Phyllactinia guttata were documented on host leaves.
• Histological examination of leaf tissues was performed to assess host-pathogen interactions and penetration points.

Main Results:

• Ascocarps of both Microsphaera pulchra and Phyllactinia guttata were found on both C. florida and C. amomum leaves, sometimes occurring together.
• M. pulchra ascocarps were denser on C. florida, while P. guttata ascocarps were more frequent on C. amomum.
• Histological studies indicated limited host penetration, suggesting ascocarps may settle on leaves rather than result from direct infection by both pathogens.

Conclusions:

• Accurate identification of powdery mildew pathogens requires a multi-faceted approach, including ascocarp morphology, host-pathogen interactions, and distribution patterns.
• The study highlights the importance of distinguishing between M. pulchra and P. guttata for effective disease management in dogwood species.
• Airborne dispersal and settling of ascocarps are likely mechanisms for the observed presence of both fungi on the studied dogwood leaves.