Cephaleuros virescens

Cephaleuros virescens is a unique parasitic green alga belonging to the order Trentepohliales. Unlike most algae, it has adapted to a terrestrial lifestyle, colonizing the surface of leaves, stems, and fruits of various woody plants in tropical and subtropical regions across the globe.

Taxonomically, it is classified within the division Chlorophyta. The pathogen is the causal agent of a disease commonly referred to as algal red rust. It has a broad host range, causing significant economic losses in crops such as tea, coffee, citrus, cocoa, avocado, mango, and various ornamental plants.

The life cycle of the pathogen is centered on the production of biflagellated zoospores. These spores are dispersed primarily by rain splashes and wind. Upon contact with a susceptible host, they germinate to form a multicellular thallus. This structure penetrates the plant's cuticle and epidermis, forming orange-brown, velvety patches that are the hallmark symptom of the infection.

Environmental conditions play a decisive role in the disease development. High humidity, frequent rainfall, and stagnant air within the plant canopy are critical requirements for the proliferation and spread of Cephaleuros virescens. Conversely, dry conditions significantly hinder the germination and infection processes of the algal zoospores.

The damage caused by this pathogen includes tissue necrosis, chlorosis, and premature defoliation, which ultimately weakens the host tree and reduces fruit quality and overall yield. Management strategies should focus on cultural practices such as pruning to enhance airflow and light penetration, ensuring proper plant nutrition, and applying copper-based fungicides when environmental conditions favor disease outbreak.