Strategies against herbicide resistant black-grass (Alopecurus myosuroides Huds.)

Black grass weeds are a problem that is increasing in Sweden. Black grass quickly develop resistance to selective grass herbicides. Future strategies against black grass must contain other forms of control than only chemical herbicides. This project investigates what impact different combinations of cropping measures, such as tillage, choice of crop in the crop rotation and selection of chemical herbicides, have on the population developments of black-grass. The experiments are placed on both locations with presumed or confirmed herbicide resistance as on field with presumed normal sensitive population. The effect of cropping measures on the presence of black-grass is determined by the usual assessments of the number and weight. The development of reduced sensitivity and resistance to various herbicides in the populations are followed by studies in which the seed samples collected from the field trials are tested in growth chambers and greenhouses. The growth chamber germination of seed samples are studied on filter paper in Petri dishes with addition of different concentrations of herbicides. In greenhouse tests the black-grass samples are sprayed under practice -like conditions and their sensitivity to herbicides are determined and compared with international reference samples of black grass where susceptibility and resistance level is known. The proportion of seeds with reduced sensitivity or resistance to various herbicides becomes an indication of the tested control measures effect on the resistance situation of the black-grass population.

The aim of this project is to develop a basis for how different actions can be combined in a system of integrated weed control where a high control of black grass can be combined with an effective strategy against the building up of herbicide resistance .

Project leader: Anders TS Nilsson
Collaborators: Allan Andersson and David Hansson
Partners: Henrik Hallqvist Swedish Board of Agriculture.

Funding: Swedish Board of Agriculture and Bayer CropScience