Potential concerns for adverse effects of trunk injection on tree health have arisen because of the injury caused by injected holes and chemical injections. There are, however, few previous reports evaluating injury formed in sapwood. In this study, we investigated the size of sapwood discoloration following injection of 4 or 2 insecticides to the trunks of Cerasus × yedoensis, Platanus × acerifolia, and Liriodendron tulipifera. The insecticide D, containing organic solvents, initiated the discoloration more than 500 cm above the injected holes in C. × yedoensis, and more than 100 cm above them in P. × acerifolia. At the height of the injected holes, it presented large cross sections of the discoloration. Meanwhile, the discoloration was largest by the insecticide B and smallest by the insecticide A among 3 insecticides using water as a solvent although they were appreciably smaller in comparison with the insecticide D. Our study revealed that the discoloration following trunk injection was largely affected by the solvents and its sizes were different among the tree species.

On the London plane tree (Platanus×acerifolia) planted as a street tree and afforestation tree, a disease is observed that the cortex and epidermis on the trunk and branches are repeatedly rising and undulating. It is gradually darkened and shows the zonate symptoms. It finally turn into the canker symptoms, and the diseased trees are forced to be hewed down. In 2017, an isolate of fungus obtained from the symptom, which had been cultivated in rice- and wheat-bran medium, was inoculated in artificially wounded trunks of London plane trees. The original symptoms were reproduced, and the inoculated fungus was re-isolated from the lesion. This causal fungus of canker disease of London plane tree was identified as a new species of Diatrypella from the morphological characteristics and molecular phylogeny, and was described as Diatrypella japonica.

Cerasus kumanoensis is a wild species of cherry published in 2018. It is distributed in Nara, Mie and Wakayama prefecture in the southern part of the Kii Peninsula, and thought to be closely related to C. leveilleana. Since the high ornamental value of flowers and the topicality of new discovery, the ornamental use is greatly examinated. However, it must be used appropriately for the conservation of wild populations. Therefore, the problems concerning conservation and utilization were summarized by using the results of distribution survey and hearing for the persons concerned. The genetic pollution and the reproductive interference by invasive cherry species with overlapping flowering period such as C.×yedoensis ‘Somei-yoshino’ and C. speciosa was thought to be the most serious problem concerning the conservation. In addition, the gene disturbance by saplings spreading and incorrect use due to lack of knowledge were concerned. Therefore, I propose a guideline focusing on the conservation of habitats, producing and using of locality-certified saplings, and educational activities by local residents. In addition, in order to promote locality-certified saplings, the usage of traceability saplings showed information about production was considered effective. Also, since there are rich diversity in wild species, breeding which selects good characters and strong resistant to pests was considered important for the sustainable useage.