Long-distance spreading speed and trend predication of fall armyworm, Spodoptera frugiperda, in China.
Fall armyworm Spodoptera frugiperda, a dangerous invasive species in the world, was found at Jiangcheng, Yunnan Province, China firstly in January, 2019. It infested 22 provinces and 0.553 million ha at July 5th, 2019. Exploring its expansion pattern is important to prevent S. frugiperda spread and its management. Based on collected data, linear distance methods were used to reveal the spreading speed of S. frugiperda in China as 14.03-14.78 km/day. Models described the relationship between number of infected provinces, number of infected counties, area of infected land and duration after invading the mainland China are presented as Yp=e(0.4235+0.0156 T), Yc=e(2.9857 + 0.0237 T), and Ys=e(-2.4312 +0.0364 T), respectively. Based on the three models, S. frugiperda will infect about 30 provinces at middle of July, more than 2 300 counties at end of July, and about 5 million ha of corn, sugarcane, and other hosts in early of September, 2019.