EFFECT OF HERBICIDES ON SEEDLING GROWTH, HEAD DEFORMATION AND GRAIN YIELD OF SPRING WHEAT CULTIVARS
In field experiments at Charlottetown, P.E.I., five herbicides evaluated at two rates of application on eight spring wheat (Triticum aestivum L.) cultivars showed no effect on dry plant weight 20 days after treatment. Herbicide treatment with dicamba resulted in a greater number of deformed heads per plot compared with the untreated in 1980 and with all herbicides except diclofop-methyl in 1981. More deformed heads occurred with dicamba and the 2,4-D/mecoprop/dicamba mixture at the higher rate of application in 1981 than with the other herbicides and the lower rate of application. All cultivars had more deformed heads than the untreated control when treated with 2,4-D, dicamba and the 2,4-D/mecoprop/dicamba mixture in 1981. Neepawa and Dundas had more deformed heads than the other cultivars when treated with MCPA. Head deformation by herbicide treatment had no adverse effect on grain yield in this study.Key words: Spring wheat cultivars, herbicides, head deformation, 2,4-D, MCPA, dicamba, diclofop-methyl