Cold hardiness of the invasive fall armyworm, Spodoptera frugiperda in China

Fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797), a crop pest native to tropical and subtropical regions of America, has invaded and spread into most regions in China, posing a severe threat to China's agriculture. The cold hardiness directly determines its geographic distribution through adapting to winter temperatures of different regions. Here, we measured supercooling points and lethal time (LT) at low temperatures of S. frugiperda. The supercooling points for developmental stages in increasing order were: adults (-15.05 degrees C)<pupae (-13.25 degrees C)< prepupae (-10.50 degrees C)< larvae (-9.03 degrees C). Among eggs and 1st to 4th instar larvae, the 99% lethal time (LT99) was the highest for 4th instar larvae, with 99% of larvae dying after 18.59 d at 2 degrees C, 58.72 d at 7 degrees C, and 66.28 d at 13 degrees C. LT99 was the lowest for eggs with LT99 of 5.33 d at 2 degrees C, 9.28 d at 7 degrees C, and 12.97 d at 13 degrees C. This study provides an understanding of overwintering regions of S. frugiperda in China, which will be helpful for population forecasting and management.