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Get started controlling resistant pigweed

Feb 12, 2008 10:16 AM, By Ford L. Baldwin
Practical Weed Consultants, LLC.

I ran into my favorite Monsanto representative at a recent meeting and we were discussing a recent article I wrote on glyphosate resistance.

I mentioned that some felt it was Monsanto’s fault that the resistance had developed. He reminded me in a friendly way about all the articles I wrote years ago about “a pint of Roundup every Monday morning until there was nothing left but soybeans.”

I sure have not forgotten them, and I guess we could argue from now to eternity whether reduced rates contribute to resistance and if so to what extent. At this point it does not really matter.

The primary factor that has caused the development of glyphosate resistance is simply the overuse of a technology that is so good that growers had little choice.

I wrote the entire winter of 2005 about glyphosate resistance at a time it was getting little attention among weed scientists. In those articles I stressed the fact that resistance to glyphosate would be different than resistance to any herbicide we had encountered previously.

Roundup Ready changed the entire farming system for most farmers. It brought an increased efficiency with it that allowed a lot of farmers to stay in business through some lean times.

The scary part of glyphosate resistance is potentially losing that efficiency and having to go back and fight weeds we had no good answers for before the introduction of Roundup Ready. Roundup Ready allowed a lot of the conservation tillage systems for the first time and drilled soybean systems that farmers had been trying to work for years.

It also provided control of weeds such as sicklepod and Palmer pigweed that we had no good answers for. A single herbicide would control almost every weed species in a field — increasing efficiency. We cannot afford to lose all of the efficiency that the Roundup Ready technology has provided.

Some weeds that develop resistance to glyphosate will be controlled by changing herbcides or adding herbicides to the system. The scary one is Palmer pigweed. We do not have it yet to the extent they do in some of the southeastern states. In some situations there, the Roundup Ready technology has been rendered useless.

I am not sure we can keep it from happening in the Mid South, but we have to try and only farmers can do it.

The mono-crop systems such as continuous cotton and continuous soybeans or wheat/soybeans are the most vulnerable. With good commodity prices on most crops now, there are better rotation opportunities, though I realize input costs vary by crop and things are never as simple on the farm as I make them sound.

If, however, you have Palmer pigweed in your weed mix and you have been in a mono-crop system, your best opportunity in the fight is to get corn or grain sorghum in those fields. Several herbicides in those crops allow you to achieve 100 percent pigweed control if you get after them hard enough.

As I stated in a recent article, some new technology is coming, but you cannot sit back and wait with Palmer pigweed. The LibertyLink technology gives us the best chance to maintain the high efficiency systems the quickest.

LibertyLink/Roundup Ready stacked trait crops being developed will allow you to rotate herbicides. Liberty is not quite as good as glyphosate on a susceptible pigweed but is a lot better on a resistant one! The LibertyLink technology is being ramped up, but it is still going to take time.

Other stacked traits are being investigated with both glyphosate and Liberty. Some of them sound really good if they work out, but you need to take action now or Palmer pigweed may put you out of business before they get here. Some of the stacked traits being worked on at this point sound a lot better for my drift investigation business than for the farmer.

Time will tell and that will be stuff for a future article.

e-mail: ford@weedconsultants.com