Ipomoea rust

The pathogen Coleosporium ipomoeae belongs to the kingdom Fungi, phylum Basidiomycota, class Pucciniomycetes, and genus Coleosporium. It is an obligate parasite that specifically affects plants within the Convolvulaceae family, significantly impacting various species of morning glory (Ipomoea) and sweet potato crops.

The disease manifests as the development of conspicuous, bright orange or yellow pustules, primarily on the abaxial side of the leaves. These structures contain urediniospores, which are easily disseminated by wind currents, leading to rapid disease spread throughout the crop. Severe infestations often lead to chlorosis and premature defoliation.

The biological cycle of this rust fungus is heteroxenous, frequently involving an alternation between hosts. While the uredinial stage occurs on Ipomoea, the fungus often utilizes conifers, such as pine trees, as alternate hosts to complete its complex reproductive cycle and survive during dormant winter periods.

Development and spread of the pathogen are highly dependent on environmental conditions, particularly high humidity, leaf wetness, and moderate temperatures. Under these favorable conditions, spores germinate rapidly, and the infection cycle repeats, potentially causing significant localized outbreaks in garden settings and commercial fields.

The economic impact of Coleosporium ipomoeae is notable due to the reduction in photosynthetic efficiency, which translates to lower plant vigor and decreased yield for tuberous crops like sweet potatoes. Management and control strategies focus on:

• avoiding planting near alternate coniferous hosts
• sanitation practices including removal of infected plant debris
• improving air circulation within plant canopy
• application of appropriate fungicides, such as triazoles or copper-based treatments, during the early onset of symptoms