With our rice planting still on-going, we wanted to remind everyone about the importance of following the herbicide label and rice seed agreements regarding Provisia and Max-Ace rice cultivars.
Both Provisia and Max-Ace are quizalofop-resistant cultivars, but they require a specific tradename herbicide to be applied legally and safely. In Provisia rice, Provisia herbicide is labeled for use. In Max-Ace rice, Highcard herbicide is labeled for use. They cannot be mixed and matched (i.e., Provisia herbicide CANNOT be sprayed on Max-Ace rice and Highcard CANNOT be sprayed on Provisia rice).
Outside of labeling laws, it is also important to abide by these rules due to rice sensitivity to the herbicide active ingredient quizalofop. Highcard herbicide has a safener to help safen Max-Ace rice (regardless of if it’s the variety or hybrid) from injury, whereas Provisia herbicide contains no safener. Provisia sprayed on Max-Ace rice, especially in cool and wet conditions, can lead to substantial injury. This was recently observed in a field by Dr. Connor Webster, Rice Extension Weed Specialist at Louisiana State University, which you can see in his tweet below. For more details on this specific case, check out our Weeds AR Wild podcast episode this week in which Dr. Webster joined us to discuss this topic along with other rice weed control advice from Louisiana:
It is important to note this distinction as we have been told there is a potential shortage of Highcard herbicide for 2022 (as is the case with many herbicides this year). If you are or were planning on planting Max-Ace rice, make sure you also have access to or have in-hand the Highcard herbicide that goes with it. Otherwise, you will be unable to take advantage of the technology. For those planting Provisia rice, there is no reported shortage of Provisia herbicide, so you should be in the clear.
For both systems, it is recommended to apply the quizalofop (Provisia or Highcard) herbicide at 15 fl oz/acre sequentially. The first application should occur at roughly 2-3 leaf rice with the second application occurring at 5-6 leaf rice (preflood). If broadleaf or sedge herbicides are also required, it is recommended to mix those herbicides with the Provisia/Highcard in the first application. More information on herbicide mixtures and antagonism with Provisia/Highcard herbicides was also discussed in the previously mentioned podcast with Dr. Connor Webster, so make sure to check it out! Finally, as a reminder, a strong, overlapping residual herbicide program is also still key for successful, long-term weed management and delaying the evolution of herbicide resistance.
As always, if you have any questions, please don’t hesitate to get ahold of us, and good luck out there!