For the past two seasons we have experienced wet springs. At the time I am writing this article we are rained out of planting our rice weed control plots, so it appears we may be headed for another rainy rice planting season. This is good news if you are growing Clearfield Rice and using Newpath herbicide.
Newpath is a moisture-loving herbicide. As you know by now, the Clearfield system calls for two 4 ounce per acre applications of Newpath for effective red rice control. Whether you are applying it prior to planting, incorporating it prior to planting, applying it after planting (pre-emergence) or making your first application post emergence, one of the keys to success with Newpath herbicide is to get an activating rainfall after making the first application. Most of the failures I have been called about (there have not been too many) have been where the first Newpath application was not adequately activated by either rainfall or flush. The first Newpath application sets up the red rice and other weeds for the second application around 14 to 21 days later to finish the weeds off. In addition, Newpath will make some weeds sick and eventually unable to survive when the permanent flood is established. Typically if red rice turns yellow and is stunting either when it first emerges following a soil application or 14 days after a postemerge application, you know you got it. When it comes up and is green and growing you may have missed it with the first application. In this situation you still have another application, but getting 100 percent control may be out of reach. In these situations a third application of Beyond herbicide will likely be needed to prevent out-crossing.
During the development of Newpath herbicide for Clearfield rice there were several years where it did not rain all spring. These years gave us examples of what might happen if the first application of Newpath is not activated. That is why a flush is recommended across the board following Newpath applications. If red rice emerges following an application of Newpath and the seedling is allowed to establish a larger root system prior to herbicide activation, then it becomes harder to control.
Newpath failures occur more often when the first application of Newpath is made pre-emergence and no rainfall occurs or the field is not flushed. Applying Newpath pre-plant incorporated can buy you a few days, but the field will still need to be flushed if it does not rain. Since the introduction of CL161 and Clearfield XL8, which have a higher tolerance to postemerge applications of Newpath, the sequential POST program for Newpath has gained popularity. Although, these applications are typically made after the red rice has emerged, a rainfall or flush is still needed to activate the soil and residual aspects of Newpath. However, later in the season when these postemergence applications are made, the levees are typically already pulled and the rice may need to be flushed anyway if it has been dry. Newpath performance is better if the weeds are actively growing and not moisture-stressed at the time of application. So, even with the sequential POST option, good soil moisture is still required to reach 100 percent control of red rice and other rice weeds.
Thus far, the Clearfield system has resulted in some of the cleanest rice fields out there, especially at the end of the season. Do not let this fool you into thinking the system is foolproof. In Arkansas, I have had several farmers tell me that we are never more than a few days away from a drought. If the rains let up and it turns dry, be ready to start the wells.
Bob Scott is the University of Arkansas Extension weed specialist. e-mail: firstname.lastname@example.org