First report of occurrence of corn and rice strains of fall armyworm, Spodoptera frugiperda in South Sumatra, Indonesia and its damage in maize

Spodoptera frugiperda is a new invasive pest in Indonesia and its severity in maize ranges from 26.50 to 100%. However, information on the strains or genetic diversity of the S. frugiperda in Indonesia is still very limited. This research aimed to identify the genetic diversity of S. frugiperda from South Sumatra and determine its damage in maize. Surveys from January to June 2021 were carried out from the lowlands to highlands of South Sumatra. The field scouting was performed to calculate the incidence of damage and to estimate the severity caused by S. frugiperda larvae. The severity was assessed using a visual rating scale from 1 (no damage) to 5 (plant stunting and funnel damaged severely). The S. frugiperda larvae was identified based on morphological characters and molecular techniques using sequence analysis of Cytochrome c Oxidase subunit I (COI) gene. All larvae collected from South Sumatra showed identical morphological characteristics identified as S. frugiperda. The sequence analysis results showed that the 6 isolates of S. frugiperda shared 100% of sameness as the rice strain haplotype 1, S. frugiperda isolate from Lampung Province. The other 3 isolates of S. frugiperda shared 100% sameness as the corn strain haplotype I and IS 1 (obtained from sugarcane in Japan). All isolates have been deposited in the GenBank. This study confirmed the presence of rice and corn strains of Spodoptera frugiperda and this is the first report of the occurrence of both strains in South Sumatra. We also found that outbreaks of S. frugiperda have occured in the South Sumatra. The incidence and severity of S. frugiperda reached 100% and 65% respectively. Comprehensive further study should be performed to confirm the presence of both strains and their damage in all corn producing areas in Indonesia.