April 2017 Update

Tripleurospermum perforatum

20 verified cases. Most of these cases are seed samples sent by farmers or consultants on suspicion of resistance. They have been tested in pot experiments including a susceptible and resistant reference population. Tribenuron-methyl and florasulam have been applied in 4-6 doses. A survey on untreated plots in agricultural fields all over Denmark showed that T. inodorum was resistant in 1% of the fields. 

 https://doi.org/10.1111/wre.70062 

 Divergent Target- Site Substitutions at Pro197 Confer Variable Degrees of Resistance to Tribenuron- Methyl and Florasulam in Tripleurospermum inodorum Populations Across Europe 

 Kateřina Hamouzová¹ |  Pavlína Košnarová¹ |  Madhab Kumar Sen¹|  Soham Bhattacharya¹         |  Michaela Kolářová¹ |  Lena Ulber² |  Dagmar Rissel² |  Björn Ringselle³|  Wiktoria Kaczmarek-Derda⁴ |  Pavel Hamouz¹          |  Josef Soukup^1 1Faculty of Agrobiology, Food and Natural Resources, Department of Agroecology and Crop Production, Czech University of Life Sciences Prague, Prague, Czech Republic | ²Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Field Crops and Grassland, Braunschweig, Germany | ³RISE Research Institutes of Sweden, Division of Bioeconomy, Department of Agriculture and Environmental Engineering, Borås, Sweden | ⁴NIBIO, Norwegian Institute of Bioeconomy Research, Division of Biotechnology and Plant Health, Department Invertebrate Pests and Weeds in Forestry, Agriculture and Horticulture, Ås, Norway

Correspondence: Kateřina Hamouzová (hamouzova@af.czu.cz) 

Received: 31 July 2025 | Revised: 14 December 2025 | Accepted: 19 December 2025  

Academic Editor: David Comont (david.comont@rothamsted.ac.uk)  

Keywords: ALS mutation | Czech Republic | florasulam | Germany | Norway | Sweden | tribenuron   

ABSTRACT Tripleurospermum inodorum (L.) Sch. Bip. is a widespread weed in cereal production systems across Europe and has evolved re- sistance to acetolactate synthase (ALS)- inhibiting herbicides in several Northern and Central European countries. This study identified and characterised resistance to the ALS- inhibiting herbicides tribenuron- methyl and florasulam in eight populations of T. inodorum from the Czech Republic, Germany, Norway and Sweden. The two Czech populations, with Pro- 197- Gln + Pro- 197- Ala substitutions in one population (CZ1) and a Pro- 197- Thr substitution in the second population (CZ2), differed in their response to tribenuron- methyl: CZ1 showed low resistance (resistance factor, RF: 5.2), while CZ2 exhibited high resistance (RF: > 53). However, both showed similar and low resistance to florasulam (RF: 2.5 and 3.9, respectively). The two German populations also showed contrasting responses: one population, with a Pro- 197- Leu substitution, exhibited low resistance to both ALS inhibitors (RF: 2.8 for tribenuron- methyl and 3.3 for florasulam), whereas the other population, with a Pro- 197- Thr substitution, displayed high resistance to both herbicides (RF: > 53 and 12.9, respectively). Norwegian populations with a Pro- 197- Tyr substitution and Swedish populations with Pro- 197- Thr or Pro- 197- Gln substitutions exhibited high resistance to tribenuron-m ethyl (RF: 15.2–> 53), but only low resistance to florasulam (RF: 2.5–4.8). Geographic patterns in substitution types were evident, with Nordic populations predominantly exhibiting polar substitutions and Central European populations showing a mix of polar and non- polar substitutions, suggesting divergent resistance evolution pathways. Notably, except for the Pro197Gln mutation, all other identified mutations have not been previously reported in T. inodorum. Overall, these results highlight the need for region- specific resistance management strategies.