Effects of the Continuous Cropping of Soybean Plants on the Occurrence of Soybean Pod Borer, Leguminivora glycinivorella（Lepidoptera: Tortricidae）

Abstract

We investigated the number of Leguminivora glycinivorella（Matsumura）adults using a sex pheromone trap and the abundance of infested seeds in soybean fields in Niigata Prefecture. The examined fields were uplands converted from rice paddy fields and are almost continuously used for cultivating soybean. The investigation was initiated at 6 fields in 2011 and continued until 2015. However, fields converted to paddies were excluded from the observation, and new soybean fields were included. Fluctuations in the numbers of captured adults of L. glycinivorella were similar between the fields and years, that is, capturing of adults began in the middle of August and ended in the end of September, and the peak period was from the 6th pentad of August to the 2nd pentad of September. The total number of captured adults and the percentage of infested seeds differed between the fields and increased with the number of years of continuous cropping. A significant positive correlation was observed between the total number of captured adults and the percentage of infested seeds. Furthermore, a significant positive correlation was observed between the percentage of infested seeds in the previous year and the number of captured adults in the present year. These results suggest that the number of years of continuous soybean cropping and the percentage of infested seeds in the previous year could be used as parameters for forecasting the abundance of this pest.