Below are a few observations from Dr. Eric Prostko’s corn research plots this week. Dr. Prostko is the Extension Weed Specialist with corn responsibilities.
2) Question #1: Why do I have Prowl H20 3.8SC (pendimethalin) mixed with everything in these treatments?
Texas panicum/buffalograss/bullgrass is one of the most common annual grass weeds in Georgia field corn. Put very simply, Prowl provides the best residual control of Texas panicum. If growers are concerned about potential crop injury from Prowl, other residual annual grass control options include Anthem Maxx (pyroxasulfone + fluthiacet), Dual Magnum (s-metolachlor), Outlook (dimethenamid-P), Warrant (acetochlor), and Zidua (pyroxasulfone). Of these, Anthem Maxx and Zidua are slightly better on Texas panicum (but neither are as good as Prowl). FYI, Prowl should NEVER be applied PPI or PRE in Georgia field corn, only POST (labeled up to 30″ tall/V8).
3) Question #2: I have heard that Prowl will cause root damage and yield loss when applied to field corn?
A long time ago in a galaxy far far away, Prowl was used as an EPOST (spiking) treatment in combination with atrazine. Back then, this was about the only way to get reasonable control of Texas panicum. In that scenario, root pruning was more likely to occur especially when corn was planted <1.5″ deep and furrow closure was incomplete. Delaying Prowl applications allows the corn plant to develop a deeper root system (but still a good idea to plant at least 1.5″ deep and have complete furrow closure though). For many years, I have been applying Prowl POST with various herbicides and have never observed any significant yield losses.