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LibertyLink technology – where does it fit?

New technology is always exciting and usually somewhat frustrating.

Although I enjoy the rare occasion when I can afford to trade for a new pickup or new computer with more bells and whistles, getting accustomed to all the new buttons is sometimes trying. At first, it just does not seem to fit. The controls are in a different place and the seat is just not molded right. But after a few weeks, the new becomes common place and actually quite nice.

LibertyLink weed control will likely be no different for many of us. LibertyLink is the Bayer CropScience trademark for crops genetically modified to be resistant to glufosinate herbicide; which was once sold as Liberty in our part of the world, but is now sold under the Ignite trade name.

I have evaluated LibertyLink cotton, soybean, and corn at some excessive rates of Ignite at almost all growth stages to determine crop response to the herbicide. All are extremely tolerant with no visual or yield differences at rates that allow good safety margins.

Let me stop here and note that crops with the WideStrike Bt gene do have some tolerance to glufosinate, but are not LibertyLink and do not have the same level of tolerance. I have walked fields of WideStrike cotton that had been sprayed with Ignite and could not find a symptom on cotton anywhere in the field. Others did not look so good and one producer indicated spraying WideStrike with Ignite cost him almost 200 pounds of cotton in 2009. It is not an illegal application, but may not be the best idea — more about this as we discuss pigweed options.

In a recent presentation, I heard (Delta Farm Press columnist) Ford Baldwin quote Australian weed scientist Stephen Powles as saying, “If your herbicide program is working, change it.” Obviously, this was in an attempt to head off resistance before it occurs on your farm. This is excellent advice from a very wise scientist, but for most of us, Dr. Powles probably should have said, “If it is working, you will change it because it won’t work very long.”

Most of us adhere to the “if it is not broken, don’t fix it” adage much more closely. Unfortunately, many of our weed control programs are broken, or at least have some big holes, and we have been making some changes by adding residuals, rotating with other crops, and hand-weeding. These add costs and sometimes fail to fit in with our best overall farm management or marketing plans.

Will the LibertyLink system allow us to return to the convenience of the early days of Roundup Ready? Maybe in cotton because we could not spray over-the-top of cotton greater than four-leaf, but not a chance in soybean where we let the weeds grow until we found the time to broadcast glyphosate over the top a couple of times and go start working on the combine.

Despite the billboards, magazine advertisements, and general hype, LibertyLink is not the same as Roundup Ready in a different color bag or jug. They are different technologies and different herbicides and must be used accordingly.

This does not mean that one is much better or worse than the other, but if we use Ignite as we have glyphosate, we will be surprised by its lack of control on grasses and larger pigweed as well as its great control on large morning-glory, wild cotton, and small glyphosate-resistant pigweed.

And, the latter may be just the stimulus that causes us to learn to use LibertyLink technology. I have heard a dozen reasons why to not adopt LibertyLink crops. Some of these have merit, but most boil down to having to change the way we are currently doing things. Let’s take a look at some of the considerations.

Variety selection is one of the most important decisions to be made in today’s agriculture. We have conducted numerous studies trying to determine ways to make farming more efficient. In almost every study, reducing any practice that reduced yield by even the smallest amount proved to be less economical. “Select the variety and then select the technology” is good advice.

If advanced weed or insect control is available in the variety that yields best on your farm, by all means, take advantage of it. If not, farm the best variety according to its characteristics. There are many cotton farmers in the southern Cotton Belt who have never adopted the Roundup Ready Flex technology because DP 555 BG/RR yielded better than the Flex varieties on their farms.

Fred Bourland (University of Arkansas cotton breeder) and Tom Barber (Arkansas Extension cotton specialist) evaluate cotton varieties over several locations across Arkansas and then combine the data with other locations across the Mid-South. Both indicate that some of the new LibertyLink varieties have performed equal to many of the top performing Roundup Flex varieties we are planting. This makes the LibertyLink cotton system worthy of consideration for the first time in the Mid-South.

Bob Scott (UA weed scientist), Jeremy Ross (UA Extension soybean specialist), and I have tested the LibertyLink soybean varieties over the last two years and I have no reservations about the yield potential compared to the top performing varieties in the state.

Can I control pigweed better with the LibertyLink system than my current RR technology? Yes, if used correctly. No, if used like glyphosate. A pre-emergence herbicide is essential for pigweed control in both cotton and soybean. The Ignite label allows only two applications per season in both cotton and soybean. The use rate is 22 ounces per acre per application in soybeans and 29 ounces per application in cotton.

We have evaluated every imaginable combination searching for the total-postemergence silver bullet. In many instances we can achieve farmable pigweed control, but a pre-emergence herbicide makes this system much stronger and reliable.

I have just reviewed five years of LibertyLink cotton and two years of LibertyLink soybean data. In approximately 20 percent of the trials, we achieved near-perfect pigweed control with Ignite alone at labeled rates.

This same near-perfect control was realized in over 95 percent of the trials when a pre-emergence herbicide was added to the system in both crops. If the pre-emergence herbicide gets activated prior to the pigweed emergence, the first application of Ignite can be delayed a couple of weeks until the first weeds emerge. If no activation occurs and pigweeds emerge with the crop, an early application of Ignite will take out the emerged weeds and allow time for the pre-emergence herbicide to get activated. This is an advantage we do not have in glyphosate-resistant pigweed fields with the RR system.

Ignite herbicide is not translocated throughout the plant as readily as is glyphosate, dicamba, and 2,4-D. For this reason, good coverage and small weeds are the keys to success.

My fear is that glufosinate tolerance in WideStrike cotton varieties is just enough to get us in trouble. After one or two applications of glyphosate, Ignite will be used in an attempt to clean up the field and the weeds will be too large for effective control at labeled rates. Although many may be killed, some will not. Those that are not killed and allowed to produce seed are the most tolerant individuals in the population — and here we go again.

Repeated applications of a sub-lethal dose is a quick way to select for resistance to glufosinate. We could lose this technology before we learn to use it effectively.

Closer attention to off-target movement, potentially spraying the wrong field with glyphosate or glufosinate, and learning the weed spectrum of Ignite are all valid concerns. Again, this is not glyphosate technology and we will make some changes. Some of these modifications may be relatively minor in our programs, but have a major impact on the success of our weed control in LibertyLink crops.

I am excited about this new technology and feel it will make a major contribution to our overall weed control programs. It is not something that I would suggest we adopt on every acre, but certainly is something that should be considered on a portion of the farm to learn how it fits into your weed management scheme. It will be another tool to use, but hopefully, it will not be the only technology on the farm. If every acre is sprayed with Ignite, pigweed and company will soon show us a new resistant biotype.


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