There has been some different herbicide questions as of late for corn and even grain sorghum.
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. Figure 1 presents some recent research data from UGA weed scientist Eric Prostko 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 has been compared to all other newer herbicide programs for many years (Figure 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 do we really want to risk any potential increases in PPO-resistance by using Valor on a relatively minor crop in Georgia? 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.