Tropical corn rust

Physopella compressa is a fungal pathogen responsible for tropical corn rust. As an obligate parasite, this fungus relies on living maize tissue to complete its life cycle and can cause significant damage to maize crops, particularly in tropical and subtropical growing regions.

The host range of the fungus is primarily limited to Zea mays. By colonizing the leaves of the maize plant, the pathogen interferes with the plant's metabolic processes, specifically hindering the ability of the crop to convert sunlight into energy efficiently throughout the growing season.

Symptoms of the disease are characterized by the appearance of numerous small, raised pustules (uredinia) on the leaf surfaces. These pustules initially appear light yellow or tan, but as the fungus matures and produces spores, they become darker brown, causing the leaf tissue to yellow and eventually necroticize.

Environmental conditions play a crucial role in the epidemiology of the disease. High relative humidity, persistent morning dew, and moderate temperatures ranging from 20°C to 28°C create an ideal environment for spore germination and rapid spread of the pathogen throughout the field via air currents.

The economic impact of tropical corn rust is primarily driven by yield reduction caused by the loss of functional leaf area. To mitigate these losses, integrated pest management is essential:

• planting resistant maize hybrids;
• maintaining good field sanitation to reduce inoculum levels;
• practicing crop rotation;
• applying fungicides when weather conditions favor disease outbreak.