Effect of density and time of removal of volunteer canola (Brassica rapa L.) on yield loss of wheat (Triticum aestivum L.)

Field experiments were conducted at Lacombe, Alberta, in 1976, 1978, and 1979. Nonlinear regression analysis of the data indicated that initial slopes (% wheat yield loss at low canola densities) varied from 0.29% in 1979 to 2.44% in 1978. However, volunteer canola at densities of 47 (1976), 345 (1978), and 251 (1979) plants m-2 had little effect on wheat yield if the canola was removed at approximately 25 d or earlier after wheat emergence. Key words: Brassia rapa, volunteer canola density, time of weed removal