ESTUDOS EPIDEMIOLÓGICOS DO COMPLEXO DE ENFEZAMENTOS DO MILHO NO OESTE DO PARANÁ

Abstract

The corn stunt complex represents a growing phytosanitary challenge in Brazil, including the western region of Paraná, where increasing vector pressure and disease severity have been observed. This study aimed to assess the incidence of diseases caused by Spiroplasma kunkelii, maize bushy stunt phytoplasma and maize rayado fino virus (MRFV), monitor the infestation of the corn leafhopper (Dalbulus maidis), and perform molecular detection of these pathogens in summer and off-season corn crops in western Paraná. Sixteen agricultural areas were monitored using yellow sticky traps for vector capture, visual inspections of plants, and molecular analyses for pathogen detection. The highest infestation of D. maidis was observed during the second growing season, particularly in the municipalities of Cascavel and Santa Helena. However, the molecular detection of pathogens and the incidence of symptomatic plants were higher during the first season, especially in Santa Helena, where 43% of the evaluated plants exhibited typical symptoms of the complex. S. kunkelii was the most frequently detected pathogen in the first season, while MRFV predominated in samples. The data revealed significant spatial and temporal variation in vector infestation among municipalities, with a tendency for increasing populations throughout the crop cycle, peaking during the final evaluations. Despite the high infestation levels in several areas, symptom occurrence was uneven, and no direct correlation between leafhopper density and disease incidence was observed. These findings indicate that the occurrence of the maize stunting complex is influenced by multiple factors, such as inoculum pressure, hybrid tolerance, and locally adopted management strategies. Integration of vector population monitoring, visual symptom assessment, and molecular diagnosis proved essential for understanding the local dynamics of the maize stunting complex, as well as for guiding regionally adapted and sustainable management strategies.