Further Notes on the First Generation Outbreak of the Oriental Armyworm in Northern Japan, 1972

Abstract

Formerly, OKU and KOBAYASHI (1974) tried to explain the cause of the first generation outbreak of the Oriental armyworm, Mythimna separata WALKER, on grasslands of northern Japan in 1972 by assuming a mass immigration of the moths in mid May, but further investigations revealed that the assumption includes some unreasonable points. In the present paper the moth trapping records are taken into consideration in addition to re-examination of weather data and distribution of the outbreak sites, and a conclusion is reached that the moth swarms may had invaded the outbreak area at night of 12th June with the passage of a duplicated cyclonic system. The immigrants are likely to be taken off from Kiangsu province of eastern China by one of the cyclones concerned, and brought into the air-currents caused by another cyclone of remote origin, when the former cyclone closely approached to the latter while degenerating.