Control of volunteer canola in barley: effect of three herbicides applied at different cereal growth stages.

Pageau, D. and Lajeunesse, J. (2008). "Control of volunteer canola in barley: effect of three herbicides applied at different cereal growth stages.", Canadian Journal of Plant Science, 88(1), pp. 247-255. doi : 10.4141/CJPS06063

Abstract

Because of crop losses during canola harvest, the presence of volunteer plants in the next production has become common. A 3-yr test evaluated the effect of herbicide application timing on their effectiveness to control volunteer canola (Brassica napus L.) in barley (Hordeum vulgare L.) and determined the grain yield reductions of the cereal associated with the presence of volunteers. Three herbicides (2,4-DB, MCPA amine, and thifensulfuron/tribenuron) were applied at four growth stages of barley: 3-4 leaf, tillering, stem elongation and flag leaf fully emerged. 2,4-DB controlled almost all volunteers at the four growth stages of the cereal. MCPA amine applied at the 3-4 leaf stage, tillering or stem elongation gave also a good suppression of canola. However, application of MCPA amine at the flag leaf stage was less effective. Thifensulfuron/tribenuron applied at 3-4 leaf or tillering reduced the population density of volunteer canola. The effectiveness of this herbicide was reduced when the application was carried out at stem elongation or at the flag leaf stage. The application of the three herbicides reduced the biomass, seed number per plant, and germination rate of seeds produced by volunteer canola. In 2001 and 2003, the presence of volunteer canola reduced grain yields of barley when the canola densities were 24 and 39 seedlings m^-2, respectively. In 2002, canola density was 11 seedlings m^-2and no grain yield reduction was observed. It is possible to control volunteer canola when the herbicides are applied at the 34 leaf stage and at tillering. However, if the application of herbicides is delayed, the use of 2,4-DB gives efficient control of volunteer canola.