September 13, 2021
Although the Southeast is not well known for its production of sorghum, there are still quite a few acres that get planted for grain, forage/silage and recreation such as dove hunting. Consequently, it is not uncommon for me to get many questions about weed control in sorghum, and I usually conduct a few weed control trials every year just to stay on top of my game.
This past summer, with the help of an old friend from Texas A&M University and the United Sorghum Checkoff Program, I had the opportunity to take a closer look at three newer weed control technologies that will eventually help Southeastern sorghum growers in their war on weeds, especially grasses. In the past, there were no effective postemergence (POST) grass control options in sorghum. Grass weeds, particularly Johnsongrass and Texas panicum, have always been a challenge. These new, non-GMO systems have the potential to help solve this problem.
The DoubleTeam system (Figure 1) includes sorghum varieties that are tolerant to POST applications of quizalofop-P. Quizalofop-P was first registered in soybeans in the late 1980s under the trade name of Assure. DoubleTeam sorghum seed will be available from S&W Seed Partners (Sorghum Partners), and the herbicide will be sold by ADAMA under the trade name of as FirstAct. Expect to see very good to excellent POST grass control with quizalofop, but historically, it has been slightly less effective on Texas panicum than other familiar POST graminicides. However, in this scenario, FirstAct should provide significantly better control of Texas panicum that what can be currently achieved.
Ty Ty, GA 2021. Credit: Eric Prostko
The IgrowthTM system (Figure 2) includes sorghum varieties that are tolerant of the imidazolinone (IMI) herbicides and are specifically tolerant to preemergence (PRE) or POST applications of imazamox. Igrowth sorghum seed will be sold by Alta Seeds and the herbicide will be sold by UPL under the trade name of ImiFlexTM. Imazamox was first registered for use in soybeans under the trade name of Raptor in 1997. Imazamox is also sold for use in the various Clearfield weed control systems under the trade name of Beyond. With ImiFlex, grass weed size at application is critical (≤ 3”) and it is only labeled for “suppression” of Texas panicum.
Ty Ty, GA 2021. Credit: Eric Prostko
The Inzen system (Figure 3) includes sorghum varieties that are tolerant to certain ALS-inhibiting herbicides and are specifically tolerant of POST applications of nicosulfuron. Inzen sorghum seed will be available from Pioneer, and the herbicide will be sold by Corteva under the trade name of Zest. Nicosulfuron was first marketed in 1991 under the trade name of Accent. Field corn growers might remember that before the rapid adoption of RR/LL corn hybrids, Accent was the standard for POST control of Johnsongrass and Texas panicum.
Ty Ty, GA 2021. Credit: Eric Prostko
The future of POST grass control in grain sorghum looks better than ever. However, growers in the Southeast should remember that the big sorghum producing states (i.e. Kansas, Texas, and Colorado) will get first preference in variety development. Thus, it might take some more time before varieties that are well adapted to our region are readily available. Also, I would like to remind all growers that a program approach that includes crop rotation, cover crops, tillage, narrow rows, PRE + POST herbicides, and hand-weeding (escapes) continues to be the best strategy to control weeds and delay the evolution of herbicide resistance.
As always, good weed hunting!
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