Abstract
This study was conducted to confirm the occurrence and distribution of trifluralin (TR)- and thifensulfuron methyl (TM)-resistant biotypes of Alopecurus aequalis in northern Kyushu and their
response to several herbicides. Seeds were collected from wheat and barley fields in Fukuoka, Saga, Nagasaki, Kumamoto, and Oita Prefectures and tested for susceptibility to two herbicides. Consequently, three biotypes of TR-resistant, TM-resistant, and multiple-resistant biotypes were confirmed, and it was found that herbicide-resistant biotypes were widely distributed in this area. The R/S ratio of multiple-resistant biotypes collected in Asakura, Fukuoka Prefecture, was 13.1 for TR, and showed cross-resistance against pendimethalin. This biotype showed no mortality when treated at the 4–5 leaf stage with TM at a concentration four
times higher. Herbicides containing benthiocarb demonstrated
effective control against this biotype. Therefore, it is suggested that thiocarbamate herbicides are effective in controlling TR and/or TM resistant biotypes of A. aequalis.
