Linkage of the current ALS-resistance status with field history information of multiple fields infested with blackgrass (Alopecurus myosuroides Huds.) in southern Germany

Abstract

The repetitive use of herbicides as major tool to control troublesome weeds in agriculture caused an increase in resistant weeds lately, especially when Integrated Weed Management principles were ignored. In a case study approach we sampled blackgrass (Alopecurus myosuroides Huds.) in three distinctive locations for at least 3 years. Based on field infestation level, greenhouse biotests and laboratory analyses we grouped 23 fields as resistant (R), 28 fields as less sensitive (I) and 39 fields as sensitive (S) with regard to their ALS resistance status. Field history information was collected for 90 fields. Variables regarding the frequency of 1) summer crops, 2) winter cereals, 3) ploughing, 4) herbicide use, and 5) early versus late seeding were calculated. Fields with a higher frequency of summer crops, ploughing and later sowing dates in the crop rotation were less frequently grouped into R and I. No relationship was found between the number of modes of action used and the resistance status. Intensity of ALS-inhibitor use and use of grass herbicides played a role to distinguish resistant from sensitive fields. Our results suggest that cultural measures to bring the blackgrass population size to lower levels are more important than the selection by the herbicide.

Keywords

• ACCase inhibitors
• ALS inhibitors
• blackgrass
• Germany
• herbicide resistance
• Integrated Weed Management