Common Cocklebur (Xanthium strumarium) Control with Reduced Rates of Soil and Foliar-Applied Imazaquin

Field studies were conducted to evaluate common cocklebur control in soybean with imazaquin applied preplant incorporated (PPI), preemergence (PRE), and postemergence (POST) at rates ranging from 24 to 140 g ai ha-1. With logistic regression analysis, predictions of common cocklebur control with imazaquin at 140 g ha-1ranged from 92 to 95% (PPI), 87 and 92% (PRE), and 88 to 98% (POST) when rainfall was received for activation of PRE treatments and when weeds were not moisture stressed at time of POST application. When imazaquin was reduced to 70 g ha-1under the same conditions, weed control was no higher than 88% PPI and 78% PRE. For all locations and years, common cocklebur control ranged from 79 to 91% for imazaquin POST at 24 g ha-1. Soybean yield was positively correlated with common cocklebur control (r = 0.66, P < 0.05).