INFLUENCE OF CLOPYRALID ON SEVERAL YIELD AND QUALITY CHARACTERISTICS OF ALTEX, CANDLE AND REGENT RAPESEED

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Abstract
The influence of clopyralid applied postemergence at several rates (0.0–0.9 kg/ha) and growth stages (two-leaf, four-leaf and pre-bud) on several yield and quality characteristics of rapeseed (Brassica campestris L. ’Candle’ and Brassica napus L. ’Altex’ and ’Regent’) was studied in the field at Lacombe in 1981 and 1983. The data were subjected to a complete factorial analysis of variance. Regression analysis indicated that for each 0.1 kg/ha increase in the rate of clopyralid, rapeseed yield decreased by 1.85 ± 0.48 g/m2. There were no effects on Candle yield due to stage of application; Altex and Regent yields were lower following application at the pre-bud than the two-leaf stage. As the rate of clopyralid was increased there was an increase in the 1000-kernel weight of the seed of rapeseed the magnitude of which varied with the cultivar. The percent germination of the seed was reduced by clopyralid applied at 0.6 kg/ha at the four-leaf stage and by 0.6 and 0.9 kg/ha at the pre-bud stage. Clopyralid did not affect the erucic acid or protein content of the seed. With clopyralid at 0.3 kg/ha there was a slight reduction in oil content (1.4%) in 1981 but not in 1983. The glucosinolate content of Altex and Regent was increased slightly with clopyralid at 0.9 kg/ha. At the proposed use rate of 0.2–0.3 kg/ha for control of Canada thistle in rapeseed, the effect of clopyralid on these rapeseed yield and quality characteristics was minimal.Key words: Dowco 290, clopyralid, Lontrel 360, tolerance, canola yield, canola quality