Tropical rust

Tropical rust, caused by the fungus Angiopsora zeae (often referenced in literature as Physopella zeae), is a significant foliar disease primarily found in tropical and subtropical corn-growing regions. As a biotrophic pathogen, it relies on living host tissue to complete its life cycle.

The primary host for this pathogen is maize (corn). The disease can infect the plant at various growth stages, but the impact is most severe when infection occurs early in the development of the leaf canopy, leading to reduced photosynthetic efficiency and grain yield loss.

Symptoms are characterized by the appearance of numerous small, circular to oval lesions on both the upper and lower leaf surfaces. These spots typically transition from a yellowish or pale green color to a darker brown as the fungus produces uredinia, which eventually rupture to release masses of spores.

The development of tropical rust is heavily dependent on specific climatic conditions. High humidity levels, coupled with moderate to warm temperatures, facilitate the germination and penetration of fungal spores. Moisture on the leaf surface is essential for the infection process to occur successfully.

Integrated pest management remains the most effective strategy for controlling tropical rust. This includes the deployment of resistant corn hybrids, which is the most economical approach. Additionally, growers should monitor fields regularly and consider the application of registered fungicides if environmental conditions favor a severe outbreak, ensuring the protection of the crop's yield potential.