Late Season Paraquat Drift on Rice

Prior to rice harvest and soybean desiccation we would like to present the work of Justin McCoy, a PhD candidate under the direction of Dr. Bobby Golden.  Justin’s dissertation investigated the effects of late-season paraquat drift on rice over the last four seasons.   With the increased use of soybean desiccants and the perception that the rice crop is completely mature,  Justin’s work is  informative and timely.

MSU recommends a 1 pint use rate of paraquat for soybeans desiccation.  A 1/10 drift rate of parquat or 1.6 ounces was applied in Justin’s studies at different rice growth stages.  Applications of the simulated drift rate were applied at seven day intervals starting at 50% heading through 50% heading plus 28 days or approximately one week prior to rice harvest.

In this multi year study, paraquat drift rate affected rough rice yields from 50% headed to one week prior to harvest.  Rice appeared to be most susceptible between the 50% heading to 50% heading plus 7 days timings.  Producers can expect a yield loss of 16%-19% at this timing.  It should be noted that timings as late as one week prior to harvest resulted in a 5% loss in rough rice yields compared to the untreated check.

As an alternative to paraquat, results from this study indicate that harvest aid products like Sharpen and sodium chlorate at comparable drift rates have little affect on rough rice yields at any of the application timings.