The growth of sapling of Castanopsis sieboldii and Cinnamomum camphora under different soil physical properties were investigated for 41 months beginning April 2017. The study was carried out in pot experiments. Experimental pots (EP) consisted of expanded obsidian (40% by volume) mixed with mountain sand to create soil improvement plots while control pots (C) consisted of sand media. The results showed that the trunk base diameter of saplings in EP were larger compared to C in both species, especially C. sieboldii. There were no differences in the tree height between EP and C. The length of the primary branch in EP were larger than those of C in C. sieboldii, but there was no difference between EP and C in C. camphora. The total dry weight of EP was high compared to C in C. sieboldii and no differences between EP and C in C. camphora. The number of leaves in EP were significantly larger than C in C. sieboldii, but there were no differences between them in C. camphora. The effects of soil amendments varied by tree species, and soil physical properties at the time of planting were found to affect subsequent tree growth.

We investigated the effect of trunk injection of dinotefuran at different time points (before and after the leaf opening period when eggs were laid) and distances (15 and 25 cm intervals on perimeters). In addition, the residual effectiveness after a year was investigated. The effect on eggs was significantly higher when the chemical was injected before the leaf opening period than after it or when the chemical was not injected or injected in the previous year. Additionally, the effect on larvae was significantly higher when the chemical was injected before or after the leaf opening than when it was injected in the previous year or not injected. Feeding damage was suppressed to under 10% by the chemical injection, irrespective of timing and interval distance, even though the density of eggs laid was high. To maintain a high effect of injection while reducing injuries on the tree trunk, a 25 cm-interval injection might be appropriate. The influence against nontargeted insects utilizing beech leaves was possibly limited to a single year.

Early detection of Japanese oak wilt relies on predicting attacks by the ambrosia beetle, Platypus quercivorus. We surveyed P. quercivorus attacks on a regional scale in Fujikawa, Yamanashi, Japan, from September to October 2022. We found that 125 (122 stems of Quercus serrata and three stems of Q. acutissima) out of 3,478 sampled stems were attacked in an area over 6×6 km². Attacks on 96% of stems were not followed by wilting symptoms. The probability of attack was positively correlated with five variables (i.e., diameter at breast height, number of stems in the same genet, topographic position index in a 100-m radius, host trees within a 250-m radius, and survey month); however, it was negatively correlated with elevation. Distance from the nearest infected forest in the previous year was not selected as an explanatory variable for the best model. In conclusion, P. quercivorus attacks disease-resistant host species and spreads widely without causing wilting symptoms.