Georgia Weeds: 3 Reoccurring Herbicide Questions

Planting and applying pre-emerge herbicide. ©Debra L Ferguson

Planting and applying pre-emerge herbicide. ©Debra L Ferguson

Got a few reoccurring questions over the last week, so I thought I would share a few thoughts with you:



1. I have heard that a few field corn growers have been reluctant to apply Prowl POST in field corn due to potential injury concerns, especially root pruning. 

POST applications of Prowl can cause root injury but this usually only occurs when the corn seed has been planted < 1.5″ deep and seed-furrow closure is not adequate.  With 21 years of data under my belt in Georgia, I am not overly worried about POST applications of Prowl causing unacceptable field corn injury (assuming correct application rate, timing, seed depth, etc.).  Figure 1 presents some recent research data from UGA which indicated that the addition of Prowl to Roundup + Atrazine did not reduce corn yields (note the very high yields). 

In fact, the combination of Roundup + Atrazine + Prowl has been the standard POST program that I have compared all other newer herbicide programs to for many years (Figure 2).   

Click Image to Enlarge
Click Image to Enlarge

2. What about using Valor (2 oz/A) in a pre-plant burndown before planting grain sorghum? 

That’s perfectly legal as long as the labeled 30 day replant interval is followed.  BUT, BUT, BUT, do we really want to risk any potential increases in PPO-resistance by using Valor on a relatively minor crop in Georgia?????



I have been preaching over the last few years that we need to save Valor for cotton and peanut.  Field corn and grain sorghum are the only 2 row crops where the use of a PPO herbicide is not 100% necessary.  Thus, grain sorghum growers who want to add a residual herbicide in their burndown program, especially when planting will be delayed for a few weeks, should consider adding either Dual Magnum or Warrant. 

Please remember that when Dual Magnum or Warrant are used in grain sorghum prior to planting or PRE, the seed must be treated with Concep.  

3. Balance Bean Herbicide (isoxaflutole), from Bayer CropScience, was recently registered for use on GT27 or isoxaflutole-resistant soybeans. 

Because of our herbicide-resistant weed issues, there might be some grower interest in this herbicide. But, UGA Extension (i.e. me and you) will not be officially recommending its use for now due to the fact that no efficacy/tolerance data has been collected in Georgia, adapted soybean variety data is not readily available, and the label that I have recently seen only permits Balance Bean applications in 7 Georgia counties (Atkinson, Berrien, Clinch, Echols, Evans, Lanier, and Lowndes).

I need to find out more information about these county restrictions and collect a bunch of local data before I would ever want a Georgia soybean grower to consider its use.    

Source URL: http://ugaweedscience.blogspot.com/2020/04/prowlfield-corn-valorgrain-sorghum-and.html