SC registers high circulation of the fine streak virus in corn.

The Santa Catarina Corn Monitoring Program released its latest report for the 2025/26 crop season on Monday (May 18th), indicating high circulation of the corn fine streak virus (MRFV) in Santa Catarina's crops. The survey, conducted over 40 weeks in more than 50 cultivation areas in the state, monitored the population dynamics of the corn leafhopper (Dalbulus maidis) and the presence of pathogens associated with crop stunting diseases.

According to data from Epagri, MRFV was the most frequent pathogen during the harvest, identified in 41,35% of the samples analyzed. Epagri researcher and program manager, Maria Cristina Canale, explains that although the damage caused by the virus is usually more localized and less severe than that caused by bacteria associated with stunting diseases, the high recurrence is a cause for concern.

"The fine streak virus maintained a high prevalence throughout virtually the entire production cycle, reaching nearly 80% between weeks 31 and 35. This shows that, by the end of the harvest, most of the leafhoppers were infected," he points out.

Striated mosaic virus (MSMV) appeared second among the pathogens detected, present in 17,9% of the samples. Following this are the bacterium of pale stunt spiroplasma (CSS), with 10,84%, and red stunt phytoplasma (MBSP), with 5,97%.

According to monitoring, pale stunt disease showed higher infectivity at the beginning of the season, between weeks one and ten, when it reached approximately 25% of the samples. After this period, the rates stabilized. The striped mosaic virus, on the other hand, showed more irregular behavior, with an increase in infection in the final phase of the season.

The red stunt phytoplasma, in turn, maintained a low incidence throughout virtually the entire cycle, rarely exceeding 20% ​​infectivity.

The leafhopper population increased at the end of the harvest season.

The report also identified significant changes in the corn leafhopper population throughout the 2025/26 growing season in Santa Catarina. Between weeks one and 15, insect levels remained close to zero. From week 16 onwards, however, there was a gradual increase in the population, intensifying as the crop stages progressed.

Between weeks 28 and 40, the largest population peaks were recorded, especially in week 33, when the average exceeded 100 leafhoppers per trap.

Another important moment occurred in week 20, coinciding with the start of the second crop planting in some of the state's producing regions. After week 25, the population increase became more significant, highlighting large differences in infestation levels between properties.

The western, far-western, and northern plateau regions concentrated the most critical scenarios of the harvest. In a large part of the traps installed in these areas, more than 30 insects per trap were recorded, considered the risk limit for producers. The final survey indicated a state average of 50 leafhoppers per trap at the end of the harvest.

Off-season management is recommended.

The researcher emphasizes that the corn leafhopper and associated pathogens can survive during the off-season in volunteer corn plants, known as "tigueras," which act as a green bridge for the next season. Therefore, the recommendation is to intensify the management of these plants between 30 and 60 days before sowing the 2026/27 crop, reducing the initial pest pressure on the fields.

Control can be achieved through mechanical or chemical methods, as well as by adopting practices such as synchronized planting, the use of genetically resistant hybrids, and the use of insecticide-treated seeds.

The program monitored more than 1,3 traps.

Over the course of 40 weeks of monitoring, the Monitora Milho SC Program published 36 technical reports, analyzing 1.394 traps and 1.642 laboratory samples using PCR tests to detect four corn pathogens. The work was conducted by Epagri in partnership with Cidasc and Udesc, with laboratory analyses performed at the Epagri Family Farming Research Center in Chapecó, and support from Fapesc.

According to Maria Cristina Canale, the information generated by the monitoring is fundamental to guiding regional integrated management strategies and reducing the impacts of corn stunt diseases in future harvests. "The productive sector will need to increasingly coexist with this problem, adopting integrated and regionalized actions to reduce the losses caused by the corn leafhopper," she concludes.