To control of bacterial shot hole disease of peach, early elimination of twigs suspected to occur spring canker has been practiced. However, this method is not analyzed objectively. Thus, in order to index the decision factor for implementing this method, we investigated leaves and twigs around the early eliminated area (early eliminated plot) and around the areas where poorly growing twigs remained (no- eliminated plot) about characteristics of each twig (germination rate, average leaf length, twig length, twig discoloration, withering, and browning dent of leaf scar). Although the difference in diseased leaves ratio was not observed in both plots in 2017, it was tended to be low in the early eliminated plots in 2018 ; This result may suggest that the early elimination suppresses disease leaf development. Next, we have investigated the growing conditions of twigs that had practiced or not practiced the early elimination from 2016 to 2018 in field. As a result, the germination and development of leaves in the early eliminated twigs had poor. Moreover, from the logistic regression analysis, it was found that discoloration, withering of twigs and browning dent of leaf scar were important factor to decide the early elimination.
Voss’s laburnum (Laburnum×watereri ‘Vossii’) is a deciduous ornamental Fabaceae tree. Recently, necrosis (brown to yellowish brown), often resulting in shoot blight, has been noted on the tree bark of Voss’s laburnum. The necrotic lesions often harbor sporocarps of Schizophyllum commune, and a Diaporthe species was frequently isolated in lesions without sporocarps. When inoculated on 1-year-old shoots, S. commune caused discoloration in the sapwood, and the Diaporthe caused significant necrosis in the inner bark as well, similar to natural symptoms. Alpha conidia of the Diaporthe isolates were ovate to fusiform, rarely irregular, hyaline, unicellular, and biguttulate, similar to D. eres. In a maximum likelihood tree based on six genetic loci, the isolate was included in the D. eres clade. We identified D. eres as the cause and proposed a new disease named ‘canker of Voss’s laburnum’.
Salt spray damage on street and park trees was observed after passing of strong typhoons in 2011 and 2018 in Tokyo-Bay area of Chiba city. Damage level was classified into 4 categories by eye, and the relationship between damage level in each tree species and the distance from the shoreline was analyzed. No dead tree was found, but many trees showed necrosis of leaves at the sea-side of the crown. Damage in deciduous trees was more prominent than evergreen trees, except evergreen Ligustrum lucidum and Cinnamomum camphora showing heavy damage in the both years. Difference in damage among tree species was greater than that among sites with different distance from shoreline. Although the damage levels in 2018 was heavier than those in 2011, they showed the same trend among species reflecting species’ tolerance to salt-spray.