THE CONTROL OF WEEDS IN SPRING CEREALS WITH MCPA, MCPB AND 2,4-DB

Summary. Eighteen experiments were carried out over a period of 4 years jointly by the National Agricultural Advisory Service and the Agricultural Research Council Unit of Experimental Agronomy to compare the effects of spraying spring cereals with MCPA, MCPB, 2,4-DB and mixtures of MCPA and MCPB, at two different times. The first applications was made before the cereal crop had reached the five-leaf stage and when it was judged that most of the weeds had germinated. The second application was after the crop had reached the five-leaf stage, which is the time normally recommended in Britain for the application of MCPA to spring wheat or spring barley. The earlier applications produced better crop yields and gave a better control of weeds except where conditions for spraying were unsatisfactory or where a considerable number of weeds germinated subsequently. Mild deformity of the ears of the crop occurred in some experiments following early applications of MCPA, otherwise there were no marked differences in the effect on the crop of the different herbicides at the doses used; the dose of MCPA was less than that of the other herbicides. In view of these results and the lower cost of MCPA, it is concluded that MCPA applied early is the most efficient of the treatments tested except where the risk of malformed ears occurring is not acceptable.
Le désherbage dans les céréales de printemps avec le MCPA, le MCPB, et le 2,4-DB