Distribution of Herbicide-Resistant Biotypes in Japan (Results of Survey through Questionnaire)

A survey was carried out through questionnaire in March 1989 to study the occurrence and distribution of herbicide-resistant weeds in Japan. Nine weed species in addition to Echinochloa species were found to have herbicide-resistant biotypes including three species of Erigeron, i. e., E. philadelphicus L., E canadensis L. and E. sumatrensis RETZ., which were reported at many survey sites. The distribution of herbicideresistant E. philadelphicus was recorded mainly in the Kanto district, while herbicide-resistant E. canadensis and E. sumatrensis showed a wider distribution from the Kanto district to the Kyushu district compared with E. philadelphicus (Fig. 1-3). Herbicide-resistant biotypes were first observed 5 or 2-3 years prior to the survey, in most cases (Table 2). Herbicide-resistant biotypes were mainly observed in orchards, mulberry or tea fields, along roadsides, in upland fields and abandoned fields, where paraquat was frequently applied (Table 3).