The Difference of Damage Degree of Batocera lineolata in Different Eucalyptus urophylla × Egrandis Plantations in Chongqing and Its Influencing Factors Research Using Factor Analysis

Batocera lineolata, an important stemborer on eucalyptus, affects seriously the development of fastgrowing eucalyptus plantations in the ThreeGorgesReservoirArea of Chongqing. In this paper, field investigations were conducted during overwintering period at 30 plantations of Eucalyptus urophylla × Egrandis in 2 districts of Chongqing, China, to assess the situations of occurrence and damage of the stemborer. Furthermore, based on these findings, factor analysis was applied to the analysis of influencing factors of difference in the damage degree caused by the stemborer among these eucalyptus forestlands. The results showed that the damage of Blineolata to the eucalyptus had increasing trend of the outbreak in the last two years, and significant differences in damage degree among these eucalyptus forestlands, and damage rates was 0-576% with an average of 196, which belongs to light or serious damage degree in most forestlands. The highest damage rate was 576% in Jinfeng town of Jiulongpo district. The insect density was mainly below 20 insects/plant and the trunk was mainly 1-2m. The damage of Blineolata has a certain correlations with the altitude and treeages, and the insect density was significantly positive correlated with diameter of damaged trunks, and altitude has no correlation with insect density and was significantly negative correlated with damged rate of the trunks. The factor analysis showed that the first factor accounted for 56% of the total variance, which means highway, artificial disturbance degree and insect density were the characteristic elements in influencing the pest occurrence in different forestlands. The sequence of influencing factors was highway ＞ artificial disturbance degree ＞ insect density. Moreover, for a special case in damaged forest, it is necessary to consider other influencing factors to give out a reasonable explanation in the damage degree of the pest in eucalyptus forestlands.