Influence of the bark characteristics of different walnut varieties on the damage caused by Batocera horsfieldi

To determine the effects of the physical characteristics and substances contained in the bark of different walnut tree varieties on the damage caused by Batocera horsfieldi, aiming to screen out varieties with strong insect resistance for promotion.

In this experiment, the main cultivated varieties, Xiluo No. 3, Xifu No. 2 and Xiangling, introduced into the same walnut orchard in Kang County, Gansu Province, were chosen as the research subjects, and the damage situation of B. horsfieldi on different walnut tree varieties was investigated, and the physical characteristics of the bark and the content of substances in the bark of different walnut tree varieties were measured and analyzed to explore their correlations with the damage of B. horsfieldi.

The results indicated that the numbers of grooves and emergence holes of B. horsfieldi on different walnut tree varieties were in the order of: Xiluo No. 3 > Xifu No. 2 > Xiangling. The bark hardness, thickness, roughness and xylem thickness of Xiluo No. 3 were the greatest, followed by Xifu No. 2 and Xiangling were the smallest, among them, the difference in bark roughness was the most significant. The soluble sugar content of Xiluo No. 3 was the highest, at (7.25 ± 0.51) mg/g, which was significantly higher than that of Xiluo No. 2 and Xiangling; there was no significant difference in the soluble protein content among different walnut tree varieties; the tannin, total phenol, and water contents of Xiangling were significantly higher than those of Xiluo No. 3, and did not differ from those of Xifu No.2.

The degree of damage by B. horsfieldi was significantly positively correlated with the bark roughness, soluble sugar content and soluble protein content of different varieties of walnut trees, and significantly negatively correlated with tannin, total phenol content and water content. In summary, among the three introduced walnut varieties, Xiangling exhibited the strongest insect resistance.