Management of Ambrosia trifida
Ambrosia trifida (Asteraceae – EPPO A2) is native to North America, where it is recorded as weedy in many US states. It was introduced into the EPPO region at the end of the 19th century, and it has expanded its range since the mid-1900s. Studies on eradication measures to control A. trifida were conducted in 2022 in the Republic of Korea. In replicated 2 by 2 m plots, A. trifida was treated using different methods (1) cutting of plants just above ground level, and (2) uprooting of plants, where all roots were removed from the site. In the spring of 2023, in each plot, following control of A. trifida, three different native seed mixtures were sown as well as a control plot in which no seeds were sown. These included seed mixtures of annual species (Lactuca indica, Elsholtzia splendens and Portulaca oleracea), seed mixtures of non-woody plants (Phragmites australis, Pennisetum alopecuroides and Plantago asiatica) and seed mixtures of woody perennials (Lespedeza bicolor, L. juncea and Sorbaria sorbifolia). In the late summer 2023, the number of shoots and cover of all plant species, including A. trifida was estimated for each plot. The presence of A. trifida was lowest in the uprooting treatment. The sowing of native seeds following invasion removal did not show any significant additional suppressive effects on invasion of A. trifida or increase of native species diversity. The EPPO Standard PM 9/31 Ambrosia trifida details that it is possible to achieve total control of A. trifida with a combination of chemical and mechanical means though this is most applicable to small outbreaks.
Sources
Byun C, Singh K, Hong SH, Lee J, Yoon TK, Kang H (2024) Uprooting is a promising tool to control invasive giant ragweed and recover native diversity. NeoBiota 94 311–331.
EPPO (2021) PM 9/31 Ambrosia trifida. EPPO Bulletin 51, 616-621.