Co-Applications Have Benefits

Combining Herbicides Saves Trips Across Fields Of Roundup Ready Flex Cotton

ST. JOSEPH, LA.
   Research studying the effects of using Glyphosate insecticide and plant growth regulator co-applied in Roundup Ready Flex cotton is among the projects of Dr. Donnie Miller, LSU Ag Center research coordinator for the Northeast Research Station.
   “We started looking at the Roundup Ready Flex technology several years ago, when it became obvious that producers would be afforded the opportunity to make these co-applications in with the Glyphosate and save the trips through the field,” he said. “So the Glyphosate formulation we looked at was Roundup Weathermax, and we looked at it in combination with 21 different insecticides. We made these co-applications either alone, Glyphosate plus the insecticide alone, or in combination with the plant growth regulator Mepex Gin Out, so we essentially had some plots that had a three way mix in them. To summarize that data, the two insecticides that we saw the most response from were Curacron and Lannate.”
   Those who are familiar with the two insecticides when applied alone may know they can be phytotoxic to cotton, causing some burn on the leaves of cotton.
   “We looked at 21 insecticides,” he continued. “We look at plant response at seven days after treatment and we did see some injury from some of the insecticides. We came back 14 days after treatment and injury with no insecticide was greater than 5 percent. We took maturity measurements and yield and saw no negative effects from any of the co-applications.”
   The research was conducted in 2004 and 2005.
   “Obviously we saw no huge effects,” Miller said. “We saw some injury – 10 percent injury, five percent injury. We get a lot of questions about co-applications of these insecticides. One of the concerns we have with the co-applications is about the high loaded surfactant Glyphosate formulations out there. Also, the EC, or emulsifiable concentrate formulations that some of these insecticide like dimethoate – which you use commonly around here for early season and mid season insect control – both of those formulations by themselves do a good job of cleaning out a spray tank of any residue left in the lines and nozzles. Our concern is that when you start making these co-applications of these two super cleaners, you get a pretty good compound there a mixture together that can clean residue out of the tank and cause problems.
   “We want to caution people to always make sure to start out with as clean a system as they can so they don’t run into the problems of tank mixing those together,” Miller stressed. “Another caution with these co-applications is make sure that the inclusion of an insecticide with the Glyphosate is warranted. Make sure that you have reached the threshold and you absolutely have to do something. Don’t just include the insecticide out there as insurance in case you have insects. With just one trip through the field, a lot of times, you can cause a flare-up of other insects pests that you are not targeting. Then you are dealing with a bigger problem than you had at the beginning.” Δ

Dr. Donnie Miller, LSU AgCenter Research Coordinator for the Northeast Research Station explains they started looking at the Roundup Ready Flex technology several years ago. Photo by John LaRose