Pigweed in cotton field

What's next in herbicide-tolerant crops?

Dow AgroSciences has announced the completion of the final environmental impact statement by USDA, thus passing a major hurdle towards deregulation and registration of GMO 2,4-D tolerant corn and soybeans (both Enlist and E3, tolerance to glyphosate, 2,4-D and glufosinate-Liberty).

2,4-D will control glyphosate-resistant pigweed and other tough broadleaf weeds, but it has no activity on grasses. The Enlist technology brings the added resistance management bonus of built-in tolerance to glufosinate. With this announcement, the likelihood of a 2015 launch is very high right now — at least for limited acres in the South, with cotton to follow in 2016.

Monsanto continues to plow forward full steam with the introduction of dicamba-tolerant crops (Roundup Ready Xtend). They hope to have deregulation of their cotton trait in time to sell some in 2015 and have been ramping up seed production in Arkansas on some pretty large acres.

It is possible that Xtend soybeans will also be deregulated in time for 2015; the comment period on Xtend crops was just opened by USDA, but a major hold up right now is world-wide acceptance (mainly China) of the GMO dicamba trait. This world acceptance issue will likely hold up dicamba-tolerant soybeans until at least 2016. Dicamba will control glyphosate-resistant pigweed and all the other resistant broadleaf weeds we currently have in the Mid-South. Like 2,4-D, it will not control grasses and a program approach will be need to prevent glyphosate-resistant grasses from developing under this system.

2,4-D and Dicamba are two different herbicides. Often through this regulatory process they have been referred to together as though they are virtually the same. They are both growth-regulator type herbicides. Both have a history of drift issues.

Most people know that cotton is very sensitive to 2,4-D at very low amounts, making drift or other off-target movement a problem. Soybeans are just as sensitive to dicamba as cotton is to 2,4-D. Although soybeans can tolerate some injury without yield loss early on, there is a stage during late flowering and early pod set (R1-2) that we do see yield loss in soybeans from dicamba drift, even at low rates. The injury symptoms are mainly a “cupping” of the leaves early on but can be bloom shed and misshapen pods if drift happens later. In later reproductive stages, R4-5 beans again become more tolerant to dicamba.

Less talked about are the HPPD-tolerant soybeans which will have the glufosinate and glyphosate stacked traits. HPPD chemistry is available from both Bayer and Syngenta. This technology is currently used in corn in products like Balance and Callisto. Eventually this technology will likely be stacked with dicamba and/or 2,4-D tolerance.

There are a lot of folks nervous about what will happen when these technologies are used in mass quantities across the South. As someone who looks at a lot of herbicide injury and drift fields, I am one of them. Some of these people ask, “Do we really need this technology?” My answer is yes, because it is what is next. While we are getting by, barely, with the technology we have in soybeans and cotton right now, we will need new technology soon.

If you are a cotton farmer, ask yourself, “What would I do if Liberty stopped working on pigweed?” What would you do in soybeans if the PPO chemistry (Valor, Flexstar, Blazer, Cobra) suddenly stopped working? Not to mention our heavy reliance on the mitotic inhibitors (Dual, Warrant and Zidua).

Are these new technologies perfect? Will they make it easy like Roundup used to be? No. But with no new herbicide modes of action on the market any time soon, they are what is next. If we want to continue to stay ahead of the weeds, we are eventually (possibly very soon) going to need new tools.

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