Glyphosate Resistant Conyza canadensis Occurring in Tangerine Orchards of Jeju Province of Korea

Aung Bo Bo1   Ok Jae Won1   In Kon Park2   Sug-Won Roh3,*   Kee Woong Park1,*   

1Department of Crop Science, Chungnam National University
2Syngenta Korea Jincheon Station
3Rural Development Administration Food Crop Industry Technology Service Division


Conyza canadensis is the weed species which most frequently develops resistance to glyphosate in many agricultural crop fields. The continuous use of glyphosate has resulted in the spontaneous occurrences of resistant biotypes. This research was conducted to investigate the response of suspected C. canadensis biotypes to glyphosate. Seeds of C. canadensis were collected from 18 sites in tangerine orchards in Jeju province of Korea. In the preliminary screening, 6 resistant and 12 susceptible biotypes were found at the recommended glyphosate rate (3.28 kg a.i. ha-1). The susceptible biotypes were completely killed at the field application rate whereas the resistant biotypes were initially injured but recovered 14 days after glyphosate application. This is the first case of glyphosate resistance found in Korea despite the national ban on genetically modified glyphosate tolerant crops cultivation. Extended monitoring should be conducted to understand how widely spread the glyphosate resistant C. canadensis is and to estimate the severity of this weed problem in the tangerine orchards of Korea.


This work was carried out with the support of Syngenta Korea and ‘Cooperative Research Program for Agricultural Science & Technology Development’ (project no. PJ012457032017), Rural Development Administration, Republic of Korea.

Figures & Tables

Glyphosate resistant Conyza canadensis  occurred in tangerine orchards of Jeju province of Korea.