Evaluation of 2,4-D Ester and Dicamba on Winter Canola in Oklahoma
Abstract
Winter canola (Brassica napus) is a valuable rotational crop for wheat (Triticum spp.) producers in the Southern Plains and provides opportunity to improve control of some winter annual grass weed species; however, unintentional drift of herbicide in winter wheat and pastures may cause damage to winter canola, reducing seed yields and decreasing crop quality. This study was conducted in 2011-2012 and 2012-2013 to determine the effect of simulated 2,4-D and dicamba drift on winter canola seed yield, 100-seed weight, and seed oil content when applied at various vegetative and reproductive growth stages. 2,4-D and dicamba were applied at 1/200, 1/40, 1/20, 1/10, and 1/5 of the recommended use rates for pasture maintenance at Stage 1 (leaf production), Stage 4 (flowering), and Stage 5 (pod development). Recommended use rates were 526 g ae ha-1 for 2,4-D and 281 g ae ha-1 for dicamba. Canola yield decreased with increasing 2,4-D rates at Stage 1 and Stage 4 during both growing seasons. One hundred percent yield reduction was observed following application of 2,4-D at 1/5 the recommended rate in both 2011-2012 and at 1/10 the recommended rate in 2011-2012. Yield in 2012-2013 also decreased with increasing 2,4-D rates at Stage 5 in 2012-2013. Dicamba had less effect on yield; however, some applications increased yield when compared to the control. Seed oil content decreased with increasing 2,4-D rates following application at Stage 1 and Stage 4 in both seasons. Applications of 2,4-D at Stage 5 decreased oil content at the 1/10 and 1/5 rates. Seed weight also decreased with increasing 2,4-D rates at Stage 1. In contrast, Stage 4 applications increased seed weight with increasing 2,4-D rates in both growing seasons. Stage 5 applications in 2012-2013 also increased seed weight with increasing 2,4-D rates. Applications of dicamba did not significantly affect seed oil content or seed weight for either year. This study shows that 2,4-D application has greater effect on canola yield, seed weight, and oil content than dicamba at similar rates. Yield was more affected at Stage 1 and Stage 4 compared to Stage 5. Seed weight was most affected when applications were made at Stage 4 and Stage 5, while oil content was affected differently from year to year.
Collections
- OSU Theses [15752]