Monsanto confirms nightmare scenario superweed (22/9/2005)

1.Next? Monsanto's nightmare scenario - GM WATCH
2.Investigation Confirms Case Of Glyphosate-Resistant Palmer Pigweed In Georgia - MONSANTO
3.Is Palmer pigweed next? - DELTA FARM PRESS

1.Next? Monsanto's nightmare scenario.

What's so significant about the admission from Monsanto (item 1) about the Roundup resistant palmer pigweed found infesting 500 acres of Roundup Ready cotton in central Georgia, USA, is that pigweed is considered one of the very toughest herbicide resistant weeds to deal with, and palmer pigweed can be especially tough.

Up till now Monsanto's Roundup was seen as a particularly effective means of dealing with palmer pigweed. Indeed, this was one of the selling points of Roundup Ready crops.

In an article published two years ago - "Is Palmer pigweed next?: Arkansas finds resistant marestail" - Delta Farm Press reported that for the Arkansas extension weed scientist, Ken Smith, who had just found marestail that was proving resistant to Roundup, resistant pigweed was "what really scares Smith." (item 3)

Smithwas quoted as saying that while resistant marestail "will be a real inconvenience and will cost extra money to manage", if pigweed ever became resistant, it would revolutionize how people farm.

The weed scientist described the scenario where pigweed became resistant as "frightening" - "That scares me terribly," he said.

According to Smith, if resistant pigweed showed up any time soon, "we'd be in a world of hurt. I don't know what we'd do. Whatever we ended up doing wouldn't be good. So we're trying to be pro-active and stay ahead of this coming problem."

Palmer pigweed - the form of pigweed that Monsanto has now confirmed as Roundup resistant - is a close relative to common (redroot) pigweed, but is considered even more resilient and harder to control,

In an article for corn and soy farmers, "Roundup Zaps Palmer Pigweed", Rob Reviere, a farmer in Tennessee who rotates soybeans, cotton and corn explains how "Palmer pigweed is the toughest weed we deal with."

According to Palmer, in his growing conditions, pigweed can get six feet tall. "Two years ago, I had pigweed so big in one field that it knocked belts off my combine."

According to the weed scientist, Jerry Parker, "Several other postemergence herbicides will take care of redroot pigweed, especially if it's small. But they don't do much for palmer pigweed, unless all conditions are ideal. If you miss a few plants, you'll have trouble keeping palmer pigweed contained."

While both Parker and Riviere say that Roundup Ready crops tend to yield less and so may not always make economic sense to grow, given their extra expense, Riviere thinks the economics are changed by Roundup's ability to deal with palmer pigweed - "if you don't get it before the weed is six inches tall, there isn't much that will handle palmer pigweed except Roundup."

The problem is, as Monsanto confirms below, there is now evidence that Roundup is no longer zapping palmer pigweed.

In other words, Ken Smith's nightmare scenario has already arrived and it's a particular nightmare for Monsanto.

With Roundup Ready crops constituting by far the biggest share of its GM products to have made it to market, and with little in the pipeline behind, the exponential growth of weed resistance to Roundup can only spell eventual disaster.

For the article, "Roundup Zaps Palmer Pigweed"

2.Investigation Confirms Case Of Glyphosate-Resistant Palmer Pigweed In Georgia

ST. LOUIS (Sept. 13, 2005) - Dr. Stanley Culpepper, a University of Georgia weed scientist, and Monsanto have determined that Palmer amaranth (Palmer pigweed) at specific sites in central Georgia is resistant to glyphosate, the active ingredient in Monsanto's Roundup agricultural herbicides. Numerous field and greenhouse trials completed earlier this year indicated probable resistance; however, heritability studies — to determine whether the lack of control is passed on to the next generation — are now complete and confirm this Palmer amaranth population as resistant.

"This Palmer amaranth population has tolerated extremely high rates of glyphosate applied in the field under excellent growing conditions," says Culpepper. The resistant population infests 500 acres of Roundup Ready cotton in central Georgia. Additional herbicide products have provided effective control of the resistant population. Dr. Culpepper and Monsanto are surveying the surrounding area this season to determine if this biotype has spread.

When glyphosate resistant weed biotypes have been identified in the past, they have been effectively managed with other herbicides and/or cultural practices, such as tillage. Based on the data available today, Monsanto recommends that farmers growing Roundup Ready cotton or Roundup Ready Flex cotton who have glyphosate-resistant Palmer amaranth on their farm do the following for 2006:

Use a pre-emergence residual herbicide such as Prowl

Apply Roundup agricultural herbicide plus metolachlor early post-emergence

Apply Roundup agricultural herbicide plus diuron at lay-by

In case of weed escapes, there are other herbicide products available as well. Growers should always read and follow herbicide label directions. Monsanto will continue to work with the University of Georgia to research the best options for control of glyphosate resistant Palmer amaranth and will modify these recommendations as new information becomes available.

"We have ongoing research planned to investigate Palmer amaranth management systems for a number of crops," says Culpepper. "We won't be sure what the best recommendation is until after the cotton harvest."

For growers that do not have confirmed glyphosate-resistant Palmer amaranth, Monsanto is recommending they use a pre-emergence residual that is active on Palmer amaranth, such as Prowl, in addition to a Roundup agricultural herbicide.

"Using a residual helps reduce early season weed competition and reduces the number and size of weeds when the first application of Roundup is made," says David Heering, Roundup Technical Manager. "In cotton, it is also important to add a residual at lay-by such as diuron to control weeds that emerge between lay-by and harvest."

Growers who are planting other Roundup Ready crops, such as corn or soybeans, should also use a pre-emergence residual if they have Palmer amaranth in their fields. Additionally, using the right rate of glyphosate for the right size weed at the right time is critical in an effective weed control program. The use of lower than recommended rates of glyphosate has been a contributing factor in previous cases of confirmed glyphosate resistant weeds. Growers should also consider using additional weed control tools that may be necessary for the weed spectrum on their farm.

The research on Palmer amaranth will be submitted to the International Survey of Herbicide Resistant Weeds at http://www.weedscience.com for inclusion on the official list of glyphosate-resistant weeds.

Monsanto Company is a leading global provider of technology-based solutions and agricultural products that improve farm productivity and food quality. For more information on Monsanto, see: http://www.monsanto.com

3.Is Palmer pigweed next?: Arkansas finds resistant marestail
By David Bennett Farm Press Editorial Staff
Delta Farm press, May 30, 2003 [shortened]

Resistant pigweed

Resistant pigweed is what really scares Smith. "It will be a real inconvenience and will cost extra money to manage resistant marestail. But we know that if we get in early enough with burndown with the right chemicals, marestail can be dealt with. It's inconvenient to get in 30 days ahead of planting because of weather, but we can do it."

But if pigweed ever becomes resistant, it will revolutionize how people farm, says Smith.

"That scares me terribly. We haven't seen resistant Palmer pigweed yet. But just like with marestail, I think it's a matter of when not if."

Smith says the kissing cousin to Palmer pigweed, water hemp, has already been found resistant in the Midwest.

"I wouldn't be surprised if water hemp and pigweed cross-pollinate and it shows up (in the Delta). That scenario is frightening and we're trying to scramble and get some alternative control measures available when it is found."

What do those measures entail?

"We don't know. Some researchers are meeting later this week trying to brainstorm. We need to know what the options are. We don't want to get out of conservation tillage or no-till practices. Those practices are cost saving, are beneficial to the environment and so they need to be maintained as much as possible.

"But we still may have to go to some kind of dirt scratching to get herbicides where they need to be. I'm just not sure. Hopefully, we'll have time - years - to get plot tests out and a plan devised."

If resistant pigweed showed up this year, "we'd be in a world of hurt, " says Smith. "I don't know what we'd do. Whatever we ended up doing wouldn't be good. So we're trying to be pro-active and stay ahead of this coming problem."

Go to a Print friendly Page

Email this Article to a Friend

Back to the Archive