Residual Offers Best Control

JACKSON, TENN.
   With any glyphosate resistant weed, the best control is to prevent it from becoming established, according to Dr. Chris Main, University of Tennessee Cotton and Small Grains Specialist.
   “Using a residual herbicide is the best control because once the weed is actually up, the glyphosate is not going to control it,” he said.
   Main said the majority of Palmer pigweed in Tennessee is also resistant to the ALS class of herbicide chemistry, Staple and Envoke. Farmers really lose a lot of options for over the top control when glyphosate does not kill a weed.
   “Even with technology such as a Liberty Link cotton, Ignite (glufosinate) is only going to give you partial control of pigweed taller than four inches,” he said. ”If the pigweed is less than two inches tall it’s going to do a really great job, but the key is if you’re fighting pigweed you’ve got to have a residual product out there and prevent the pigweed from becoming established in the field, which is easier said than done since residual products need rainfall or irrigation for activation.”
   Main discussed his trials the past few years with Reflex as a preemergence product in cotton production to help control pigweed populations.
   “Reflex received a federal label for cotton in 2006 as a preemergence and a layby treatment, but currently the label restricts its use to coarse textured soils, such as sandy loams, generally found on coastal plain areas or river bottoms,” he added. “So it has not been used in the Midsouth on silt loam or clay soils.”
   Main said he’s seen significant injury with it in the past, so he’s been re-investigating how it can be used. One method he’s looked at is pushing it back from planting maybe 14 to 28 days preplant with a burndown partner.
   “Using Reflex in this manner makes it perform more like an early Preplant application of Valor, giving us some residual extended into the early season to keep the pigweed out while we’re planting and waiting for the first postemergence spray,” he said.
   “We had real good results with it the last three years. There was almost no injury. Typically we can get by using it preemergence in our no-till situations without any injury because the residue helps prevent splashing of the herbicide from the soil back up onto the leaf surface.
   “However, we’re really expecting a label to have wording in there for use on silt loam soils 14 days before planting similar to the 24c label approved for Arkansas this year,” he added. “It’s going to be a real good product to have in the portfolio of the cotton producer to help provide early season pigweed control.” Δ

Discussing glyphosate resistant weeds is Dr. Chris Main, University of Tennessee Cotton and Small Grains Specialist. Photo by John LaRose, Jr.