The relationships among longitude, latitude and elevation of occurrence of Parocneria orienta (Lepidoptera: Lymantriidae) in China

Background Parocneria orienta is the primary defoliator of Cupressaceae plants in China, and its geographic range is expanding. Research is needed to identify the geographic distribution of P. orienta and its major areas of occurrence and to formulate measures for early warning, monitoring and control of this pest. Methods Data on the occurrence P. orienta were collected from 4,688 monitoring sites in Sichuan Province from 2012 to 2016. Analyses of the spatial distribution and model fit were carried out using ArcGIS and Matlab software. Results We found that the occurrence of P. orienta complied with a normal distribution law (α=1% confidence level) in terms of longitude and latitude and belonging to generalized extreme-value distribution (α=1% confidence level) in terms of elevation. According to the double factor variance analysis taking year-month as the time variance and longitude, latitude and elevation as the space variance, the hazard centroid shifted significantly by 6 minutes of longitude in March (105°46′37″E) and July (105°40′30″E) of the same year. The hazard centroid has not changed much over time in terms of latitude and elevation. Discussion The regions of greatest damage by P. orienta were in eastern and southeastern parts of Sichuan Province (105.7°E–31.1°N, elevation 400 m), an area that features plains and low mountains with lush vegetation and abundant Cupressus funebris. In March, there is little rainfall, which is beneficial for growth and breeding of larvae, and causes a rapid increase of population that then results in widespread damage to Cupressaceae plants.