Will rice-preferred fall armyworm, Spodoptera frugiperda be a new threat to rice production in China?

The fall armyworm, Spodoptera frugiperda, a significant pest, has spread to many countries in Africa and Asia in recent years, causing substantial losses in corn production. From 2019 to 2024, we monitored the host strain of S. frugiperda in various regions in Jiangsu Province, China. The result showed that only COIRS-TpiRS and COIRS-TpiCS strains were present in corn during 2019 and 2020. In 2021, COIRS-TpiRS, COIRS-TpiCS and COICS-TpiCS strains were detected in both corn and rice. By 2024, all the three strains were found exclusively in corn. Notably, the proportion of COIRS-TpiRS strain increased from 2019 to 2021, but declined in 2024. Experimental data demonstrated that COIRS-TpiRS had higher fitness on rice than on corn, and showed a preference for damaging and ovipositing on rice. However, the occurrence of S. frugiperda in rice paddies remains rare, suggesting that it is unlikely to become a significant threat to rice production in China in the coming years without change in rice planting pattern.