Autor: Carloni, Edgardo José; Carpane, Pablo; Torrico Ramallo, Ada Karina; Gimenez, Maria De La Paz; Virla, Eduardo Gabriel

Corn stunt disease caused an epiphytotic outbreak in maize production in Argentina, resulting in yield losses of up to 30% during the 2023/2024 season

The corn leafhopper, Dalbulus maidis, is the primary vector of maize disease–associated pathogens, particularly Spiroplasma kunkelii. This study evaluated the natural infection of D. maidis with S. kunkelii and the inoculation capacity of infected insects, integrating data from an endemic phase during the 2004/2005, 2005/2006, and 2006/2007 agricultural seasons with recent observations from the 2023/2024 epiphytotic in subtropical Argentina. Field surveys confirmed year-round persistence of D. maidis, with female-biased sex ratios during spring and summer. Molecular and serological analyses revealed a marked increase in S. kunkelii proportion within vector populations, rising from an average of 1.8% in 2004/2005–2006/2007 to 12.5% in 2023/2024. Logistic regression further showed that the odds of testing positive in 2023/2024 were 13.3 times higher than in 2004/2005. This coincided with a sharp increase in the disease, which reached an incidence of 97% and prevalence of 100% in the maize fields sampled in Tucumán during the 2023/2024 season. Transmission assays further demonstrated that 28.6% of infected adults successfully inoculated S. kunkelii. Together, these results update the epidemiological understanding of the D. maidis-S. kunkelii pathosystem and provide evidence that an increased proportion of infectious vectors played a central role in the recent disease epiphytotic. Monitoring infection levels in vector populations emerges as a key early-warning tool and supports the implementation of integrated management strategies to reduce disease impact.

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