ATP-binding cassette transporter C2 (ABCC2) is known to be a receptor for Bacillus thuringiensis (Bt) toxins in several lepidopteran insects.  Mutations in the ABCC2 gene have been genetically linked to field-evolved resistance to the Cry1F toxin from Bt in Spodoptera frugiperda.  Here we generated a SfABCC2 knockout strain of S. frugiperda using the CRISPR/Cas9 system to provide further functional evidence of the role of this gene in susceptibility and resistance to Cry1F.  Results from bioassays showed that the SfABCC2 knockout S. frugiperda strain displayed 118-fold resistance to Cry1F compared with the parental DH19 strain, but no resistance to Vip3A toxin from Bt.  These results provide the first reverse genetic evidence for SfABCC2 as a functional receptor for Cry1F.

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), has become an important pest in Chinese agricultural systems since its invasion on 11 December 2018.  After its establishment, FAW months in the year-round breeding region have become the main source population migrating to other areas in China.  Field investigations were conducted in tropical and subtropical regions to improve understanding of its year-round breeding area in China.  The results showed that FAW larval density was significantly correlated with the seasonal temperature of the location surveyed.  The FAW larvae maintained a high density in the tropical area and were frequently found in sites of the south subtropical region, but were absent from the north subtropical region and the northern part of the central subtropical region.  These results indicated that FAW can reproduce annually in the tropical and south subtropical regions of China, including Hainan, Taiwan and the southern area of Fujian, Guangdong, Guangxi, Guizhou, and Yunnan.  Hence, great effort should be made to monitor and control FAW in the year-round breeding region to suppress the population density of this area and to reduce migration of moths into northern parts of China.  This study clarifies the occurrence area of the pest in winter in China and provides much valuable information for its population forecasting and management.

The fall armyworm (FAW), Spodoptera frugiperda is one of the most damaging crop pests, and it has become major threat to the food security of many countries.  In order to monitor possible invasion of this pest into China, a searchlight trap was established in March 2018 in western Yunnan Province, China, where it has served as the “first station” for many pests that have migrated from Myanmar to China.  A number of suspected FAW moths were captured and identified by DNA sequencing.  The results showed that the FAW moth was first captured on December 11 and formed its first immigration peak in mid-December 2018.  DNA detection revealed that the early invading FAW population was the “corn-strain”.  The field survey indicated that the pest mainly colonized corn in Pu’er, Dehong and Baoshan areas.  Migration trajectory simulation implied that the moths might have mainly come from the eastern area in the mid-latitude region of Myanmar (20–25°N, 94–100°E).  This case study confirmed the first immigration of FAW into China, and will be helpful for guiding monitoring and management work to control this pest.