Geographic distribution of regulated viruses infecting sugarcane in Louisiana

Commodities

Practices

Sugarcane is the second largest global agricultural commodity after cereals. In Louisiana, it is grown on 212,460 hectares and contributes approximately $1.59 billion annually; however, this crop is threatened by yellow leaf disease (YLD) and mosaic disease (MD). MD is characterized by mottling and chlorosis caused by sugarcane mosaic virus (SCMV) or sorghum mosaic virus (SrMV), with SrMV historically being more prevalent in Louisiana. YLD is caused by sugarcane yellow leaf virus (SCYLV); however, the disease is often asymptomatic in Louisiana, likely because of the relatively short growing season of the state's sugarcane cropping system. Despite causing limited or no visible symptoms, SCMV, SrMV, and SCYLV can reduce photosynthetic efficiency, cane yield, and sugar production, resulting in economic losses. Spread occurs primarily through infected planting material, while in-field spread of these viruses is facilitated by distinct aphid vectors. The current incidence, distribution, and genetic variation of SCYLV, SCMV, and SrMV in Louisiana remain unclear because previous surveys are outdated and often limited to breeding fields. Therefore, our objectives are to develop a multiplex assay capable of detecting all three viruses and to test an early detection tool for monitoring their aphid vectors. Preliminary data from a 2025 survey of 30 commercial fields across 10 Louisiana parishes showed that SCYLV was detected in 93.3% of locations, while analysis of mosaic-associated viruses is still underway. Together, these efforts will provide an updated status of these viruses in the state and support targeted disease management strategies for the Louisiana sugarcane industry.

This project has three objectives:

1. A statewide survey of commercial sugarcane fields in Louisiana will be conducted to determine the incidence and distribution of SCYLV, SCMV, and SrMV. This work proves particularly important as most recent studies are decades old^3,6 and the survey indicated that SCMV was not detected in the sampled locations⁷.
2. The genetic variation of the three major sugarcane viruses present in Louisiana will be assessed. Virus isolates obtained during the survey will be analyzed using molecular approaches to identify variation among populations. This will improve understanding of the strains present in Louisiana and provide information that may be useful for tracking changes in virus populations over time using previously published work.
3. The project will assess the ability of developed computer vision models to detect and count aphids using image analysis and machine learning. Because aphids are important vectors involved in the spread of all three viruses, streamlined monitoring of vector populations in sugarcane fields is crucial. Based on the high incidence of SCYLV, this work will focus on the virus's primary vector, the sugarcane aphid.

Together, these objectives will provide information needed to support more effective and sustainable disease management strategies for Louisiana sugarcane production.