Factoring distribution and prevalence of Fall armyworm in southwest China

Host plant growth changing with environmental conditions can impact the distribution of herbivores. The generalist herbivore fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an invasive pest rapidly spreading across the world and has recently invaded southern China. We studied effects of environmental factors on the distribution of the fall armyworm and its host (maize) plant growth in the tropical mountainous area of Huize County, province of Yunnan, southwest China. Moreover, the relationships among the FAW distribution, environmental factors (altitude, temperature and humidity) and plant growth (mean kernel weight, kernel number per ear and ear weight) were analysed. The results showed that FAW predominated at altitude 1,243.3 m, temperature 21.4°C and humidity 82.1%. The host plant grew best at 1,200–1,312 m, 21.0–21.7°C and 81.2%–82.0%. Environmental factors indirectly influenced the distribution of FAW via the host plant growth. Compared with environmental factors, the host plant growth had a simplistic positive linear relationship with the density of FAW. FAW is less impacted by abiotic factors rather it determined by host plant prevalence, and thus the locations where maize plants grow best are preferred by FAW and should be the focus of insecticide applications. Understanding the distribution of FAW under various environmental conditions provides a valuable reference for Chinese maize production and food security.