A new, practical control measure of pine-wilt disease is proposed that has recently been conducted in coastal Akita, northern Japan, and the rationale is tested. The control measure aims to prevent adult emergence of disease-spreading pine sawyer Monochamus alternatus endai and reduce the population through converting damaged trees into charcoal. Pine wilt disease in Akita, northern limit of the disease in Japan, is characteristic in that infected trees are weakened and die throughout the year and that adult M. alternatus endai beetles emerge for a short period and oviposit only on the summer-weakened trees. Observation of pine logs caged in the field showed that adult emergence in Akita began late June. It is thus important to identify and exterminate summer-weakened trees before adult emergence next year. Within infected trees, M. alternatus endai larvae are distributed non-evenly; they are sparse in lower, thicker part of the stem but dense in upper, thinner parts including branches. Therefore, those thinner parts should also be gathered and exterminated. Compared to usual control measures, our method is advantageous because thinner logs and branches are fully utilized for fire making at the earliest stage of charcoal production. Moreover, diseased trees can be reused in the forms of charcoal, ash and pyoligneous acid solution, suggesting this control measure to be resource-sustainable. Charcoal making seems attractive for people, increasing voluntary members that might play a role in early finding of infected trees. Disease monitoring is necessary for further evaluation of our method.

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[in Japanese]

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We measured and analized ring width of Thujopsis dolabrata var. hondai MAKINO with images taken by digital camera, studied whether it synchronized on every sample and tried to make standardized tree-ring chronology. There were 12csamples which were collected from 6 different places, Aomori, Kanita, Owani, Kawauchi, Oma, Kanagi, in Aomori Prefecture. We measured tree-ring width of each sample for 2-4 directions by the images. Crossdating and examining whether it synchronized, we found high correlation in any sample and in any place as well. We could assign 6 different places to three areas, Aomori, Tsugaru, Shimokita, which can be divided in Aomori Prefecture and then we found synchronization in these three areas and one another area. Hence we concluded that tree-ring width synchronized throughout Aomori Prefecture. As a result of this, we could make standardized tree-ring chronology from 1759 to 1990, that is to say for 232 years, and find it useful in determining periods of relice of woods excavated from remains in Aomori Prefecture.

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[in Japanese]

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