An investigation of <i>Caligula japonica</i> (Lepidoptera: Saturniidae) egg distribution and associated parasitoids on walnut trees (<i>Juglans regia</i> L.) in northwestern China
Yong‐Ming Chen, Jia-Wei Sun, Asim Iqbal, Rui‐E Lv, Hai Wang, Lian‐Sheng Zang
Abstract
Caligula japonica is a serious defoliator pest of walnut trees, Juglans regia, in China. Important information about the occurrence of C. japonica egg masses on host plants and their indigenous parasitoids under field conditions are rarely documented. Here the distribution of egg masses of C. japonica on the trunks of J. regia and occurrence of its parasitoids in Kangxian, the most important walnut production area in northwestern China, were investigated. The results revealed that the egg masses were mainly located at 109.2 ± 62.3 cm height. The number of egg masses exhibited a significant positive linear relationship with the diameter of trees and a parabolic relationship with host tree height. The natural parasitism rate showed a significant negative linear relationship with the size of egg masses but no relationship with the height of egg masses. The percentage of parasitized egg masses and parasitism percentage of eggs were 49.0% and 7.0%, respectively. We found seven egg parasitoid species belonging to three genera, in which Mesocomys trabalae had the largest Berger-Parker index (0.6963). In addition, the coparasitism of M. trabalae and M. albitarsis accounted for 39.7% of the total coparasitized egg masses. This investigation provides basic information for utilizing egg parasitoids against C. japonica in the future.