INTRODUCTION OF A NON DESTRUCTIVE METHOD FOR THE INVESTIGATION OF HERBICIDE EFFICACY IN GREENHOUSE BIOASSAYS BASED ON IMAGE ANALYSIS

The North China Plain (NCP) is the main winter wheat growing region in China. In winter wheat, Bromus japonicus is an important annual monocotyledonous weed, which is difficult to control and causes high yield losses as a consequence for lack of effective herbicides. For this reason dose-response studies were conducted in a greenhouse to test the efficacy of several herbicides on B. japonicus. Two ACCase inhibitors, five ALS inhibitors and one PS(II) inhibitor were tested at six different application rates. Efficacy on B. japonicus was measured by dry weight assessment as well as non-destructively by leaf coverage measurements with a bi-spectral camera. The efficacy of the tested ACCase and PS(II) inhibitors was not satisfactory for weed management, even at high dosages. However the tested ALS inhibitors showed high efficacies. Coverage measurements with the bi-spectral camera correlated very well with the dry matter weight of B. japonicus. Therefore it can serve as an easy, rapid and non-destructive method to determine herbicide efficacy over time and also under field conditions. It is necessary to introduce new herbicides to the NCP for efficient weed control, to ensure the security of the national food supply. Therefore comprehensive dose-response studies are necessary to evaluate herbicides of interest with different modes of action on all important weeds of the NCP.