Temporal Changes in the MITC Gas Concentration and Mortality of the Pine Sawyer Beetle (Monochamus alternatus) Following Fumigation Treatment of Pine Logs Using the Top Covering and Complete Wrapping Methods

Abstract

In the eradication of the pine sawyer beetle (Monochamus alternatus), two types of covering methods are used for the fumigation of infested pine logs: the top covering method, which is widely used in Japan; and the complete wrapping method, which has been adopted in limited areas. To elucidate the effectiveness of the two covering methods, we measured the temporal changes in the MITC gas concentration in the coverings and evaluated the mortality of the insect larvae in the treated logs at four study sites with different soil conditions. The MITC gas concentrations peaked from 2 h to 1 day following the initiation of treatment and gradually declined toward 15th day when we terminated the census, regardless of the covering method and/or study site. High levels of larval mortality were recorded in all of the treated logs. A few larvae were found to be alive in pupal chambers plugged with tightly stuffed wood fibers in the galleries. Such chambers were formed at relatively deep positions from the wood surface. From these results, we concluded that both fumigation methods have equivalent effectiveness for eradicating the pine sawyer beetle.