Herbicide resistant Amaranthus palmeri in Japanese ports
Amaranthus palmeri (Amaranthaceae - EPPO A2 List) is a dioecious summer annual species native to North America, where it has become a weed in agricultural fields and disturbed habitats. It has a high fecundity and a long-lived seed bank which makes management of the species difficult. In the EPPO region, it is established in a few countries and transient in several others. The species can develop resistance to herbicides which can complicate the management of the species (see EPPO RS 2021/095). In a survey, 14 major Japanese ports of entry for international commodities were surveyed between August – September 2014-2017. At each port, the main road network was surveyed in an approximate 10 km radius around each port. In total, A. palmeri was recorded at five ports, and at one port up to 10 000 individuals were found growing along 1.5 km of roadside and the central divider. At three ports (Kashima, Hakata and Mizushima), herbicide (glyphosate) resistant individuals were found (resistance was evaluated using PCR and microsatellite marker analysis). This study shows that in less than ten years since the first report of glyphosate resistant individuals in the United States, glyphosate resistant plants are established in Japan. Management measures should focus on the control of this species in the areas where it currently occurs.
Sources
Shimono A, Kanbe H, Nakamura S, Ueno S, Yamashita J, Asai M (2020) Initial invasion of glyphosate-resistant Amaranthus palmeri around grain-import ports in Japan. People, Plants, Planet 2, 640-648.