Outbreaks of shoot blight of larch associated with strong rain-bearing winds caused by typhoons

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In 1981, after passing through two typhoons, localized severe outbreaks of shoot blight of larch caused by Guignardia laricina YAMAMOTO et ITO occurred in young plantations of Larix leptolepis GORD. in the coastal areas of Hokkaido. Surveys conducted in the areas facing Ishikari Bay revealed that trees growing on wind-exposed hills were infected more severely than those on wind-sheltered slopes, and trees on the windward edge of a stand also tended to show an increase in disease severity. Meteorological data confirmed that strong winds from the sea had swept the surveyed area when both of the two typhoons passed. Many investigators have proved that high temperatures, heavy rains, and strong winds which cause wounds on shoots are essential factors in determining the incidence of the disease. Especially, wounds providing entry points for the pathogen have been considered to be the most important requirement for infection. Further studies during the following year, 1982, showed that there was little incidence of this disease in the absence of typhoons. In fact, numerous recovering trees were observed, and they produced new sound shoots from near the bases of the old dead branches. Thus the localized outbreaks in the surveyed area can be attributed to the strong rain-bearing winds brought about by the two typhoons in 1981.
日本森林学会の論文