Monsanto Has Details On Their Dicamba-Tolerant Crop System

Roundup Ready 2 Xtend soybeans will come with some application requirements to ensure drift is minimized.

Published on: Sep 11, 2013

At a Monsanto Roundup Ready 2 Xtend field day in Collinsville, two things were abundantly clear.

First, glyphosate-resistant Palmer amaranth is extremely difficult to control. Second, due to the USDA requesting an Environmental Impact Statement, Monsanto's dicamba-tolerant soybean crop technology likely won't be commercially available until 2015 or later, pending regulatory approval.

Despite the bitter taste from these two points, there was a bright spot. The Roundup Ready 2 Xtend plots were clean of Palmer amaranth. That's an impressive feat, considering how bad the untreated check plots looked.

Herbicide offerings
Another bright spot was learning a bit more about how this new crop technology will work once it's released.

Monsanto Has Details On Their Dicamba-Tolerant Crop System
Monsanto Has Details On Their Dicamba-Tolerant Crop System

John Willis, technology development manager for Monsanto, explains the herbicide component of this crop system will be available in two different low-volatility formulations. The first is a pre-mixed product that includes glyphosate, dicamba and a surfactant. It's called Roundup Xtend.

Willis notes Roundup Xtend's recommended rate will be loaded with 1 lb of glyphosate and 0.5 lbs of dicamba.

If a farmer wishes to tankmix his own herbicide program, the dicamba component is available separately as Xtendimax. Willis explains the recommended rate is 0.5 lbs of dicamba per acre. Xtendimax is not loaded with a surfactant.

In trials, Willis says the dicamba component of these herbicides provided residual activity for an average of 14 days after application.

"Dicamba is water soluble, so it actually has a longer residual activity in dry soils," Willis notes.

He adds that typically residual herbicides need about a half inch of rain to work. Dicamba requires very little moisture for residual control.

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Drift concerns
Remember when glufosinate-tolerant soybeans were released? Folks quickly learned that confusing glufosinate- and glyphosate-tolerant soybeans could render disastrous results.

The same rules will apply for Roundup Ready 2 Xtend soybeans. After spraying a mixture that includes dicamba, tank cleanout is of paramount importance.

Monsanto's Seth Logan says the tank must be triple rinsed. This is in addition to taking the nozzles apart and cleaning the strainers and screens.

Logan showed some plots where the tank had been rinsed once or twice. It definitely wasn't enough.

For those who don't have time to rinse the tank three times, Monsanto is experimenting with a "deactivator" that essentially renders the dicamba ineffective. The results are encouraging.

Of course, drift is a major concern, even more so with dicamba.  There will be stringent spray application requirements for the Roundup Ready 2 Xtend crop system. One requirement is a very coarse nozzle as the minimum for droplet size. In the Collinsville test plot, ultra coarse droplets provided the best drift reduction results.

At the field day, Logan pointed out the results of spraying a dicamba mixture in a traditional Roundup Ready soybean field with an XR nozzle, which produces a high percentage of medium and fine droplets (less than 150 microns). On the day of the application, the wind was blowing at 3 to 6 mph. With that nozzle, Logan saw symptoms of drift up to 50 yards away from the edge of the treated area.

Sara Allen, a weed management technology development rep with Monsanto, says the EPA is working to establish spray buffer requirements for Roundup Ready Xtend technology. Additionally, Monsanto will release a "Spray Manager Plus" app that will help applicators establish the proper buffer zones when spraying Roundup Xtend and Xtendimax.