We detected non-destructively the internal defects of the living trees planted in the campus of Shimane University by the lateral impact vibration method, and tried the application of this method to the diagnosis of trees. In this study, we used a product of the lateral impact resonance frequency and the girth as an index of the internal defects. The trees were classified into a few groups by the frequency distribution of the index, and it could give easily recognizable results of the diagnosis. The usefulness of the lateral impact vibration method for preparatory diagnosis of living trees was proved by the index.
The damage to 501 26-year-old Chamaecyparis pisifera trees planted in a Cryptomeria japonica seed orchard caused by cryptomeria bark borer was examined. The damage by this beetle was observed on five trees. The percentage of the trees damaged was 1.0% (5/501), which was much lower than the percentage of damage in the neighboring C. japonica stands (30%). Three among the five damaged trees were dead. The percentage of dead trees was higher than that of C. japonica trees, which were rarely killed by the attack. The stem analysis of the dead trees suggested that these trees were killed by heavy attack in that or the preceding year. The capture test by adhesive bands revealed that many cryptomeria bark borers flew to C. pisifera trees, but they did not give heavy damage.
Thionazin and mesulfenfos belonging to nematicides were injected into ll-year-old Japanese black pine, diseased with pine wilt disease by the inoculation of pine wood nematode 2, 5, and 6 weeks before the nematicides treatment, with the following results. In the standing trees, the following were observed : 1) Recovery of pine resin exudation and high survival rate in the thionazin- and mesulfenfos-injected trees two weeks after the nematode inoculation, 2) Recovery from the stagnation of thickening growth in the recovered trees, 3) Partial death of trees in the recovered and survived trees, and 4) Surrounding with under-bark necrosis composed of innerbark and cambium in the base of the dead branches of the partially died trees. In the cross-section, no water conducted vascular patch or brown colored stains from pith were observed. Under-bark necrosis occurred where brown colored stains were found till the annual rings made in the year when curative experiments were conducted. The results of the curative nematicides injection experiment showed that there are two disease development stages. In the first stage, recovery from the disease can be expected with the nematicides treatment because it is reversible as cambium cells remain alive despite the cessation of pine resin exudation and the stagnation of thickening growth. However, in the second stage, the possibility of recovery with nematicides treatment falls rapidly because of the development of brown colored stains which cause the death of cambium to extent from part to the whole body.