Influence Of Apriona Germari On Tree Growth And Wood Quality Of The Pulp Forest Of Triploid Hybrids Of Populus Tomentosa And Suggestions For Its Control

Mulberry longicorn beetle, Apriona germari (Hope), is an important borer of poplar trees causing extensive damage and even mortality to pulpwood trees of triploid Chinese white poplar (TCWP). In order to know impacts on the growth and wood quality of the trees infected by A germari and provide suggestions for pest control, we conducted experiments as follows:The tree growth and quality of pulpwood of infected trees were partly examined. The damage degree in forests of 6 TCWP clones caused by larvae was investigated. The structure of the larvae gallery on TCWP were observed. The control suggestions for A. germari control were proposed according to the results of zinc phosphide sticks test. The results are as follows:(1) Limitations of the damage rating established on the larvae number were addressed. In our study, the injured trees were divided into four ratings by cluster analysis and unaided viewing based on the number of larvae and defecation holes and the length and position of galleries in the wood. This method was first used to divide the damage ratings, which is the basis of further investigation and research.(2) Comparing plant growth and volume of trees in different damage ratings, we found that tree growth was affected due to being infected by the larvae. Tree diameter at breast height increased while tree height decreased with the level of victimization, but there were no significant differences among different ratings. In addition, the net volume of trees was not affected by the larvae.(3) Comparing the papermaking material of trees from different damage ratings, we found that the chemical papermaking performance was affected by the larvae. Although significant difference was not found among trees of different damage ratings, the content of wood holocellulose gradually decreased with the increase of the damage ratings. The content of alcohol-benzene extractives gradually increased with the victims and there were significant differences, thus adversely affecting the papermaking. No difference was found in dry wood moisture content 1%NaOH extractives content of trees from different damage ratings, therefore, the damage by larvae did not affect decay resistance of wood.(4) The damage of the Apriona germari was different in various triploid clone strains. The maximum population density of overwintering land is 0.34 per tree in the B305, and the minimum is 0.15 per tree in B301. Statistical analysis showed that the larvae in the six strains land can not be clustered in the same degree.(5) The gallery structure of A. germari (Hope) larvae in TCWPis different from other hosts reported. In TCWP, the gallery of larvae was longer than 5m and the number of defecation holes adds up to 34, which were distributed in all directions of the trunks. The distance between two defecation holes mostly ranged from 0 to 20 cm.(6) Control suggestions:Low-susceptibility clones, such as B302 should be planted. Baiting trees Broussonetia papyrifera (L) should be setted according to the knowing of spatial pattern of the larvae infecting their hosts. The larvae were stopped from damaging the trunk by manually pruning branches. The Zinc phosphide sticks were inserted into new hole of the gallery from bottom to top, and then the holes had to be blocked with mud.