Glyphosate-resistant weed problems in Brazil (2/5/2007)

1.Glyphosate-resistant weed problems in Brazil

1.Glyphosate-resistant weed problems in Brazil
Globo Rural TV, 01.14.2007
(Globo Rural is a weekly Sunday TV program in Brazil about agriculture)

Transcription of the TV program is by the anti-GM campaign group AS-PTA - POR UM BRASIL LIVRE DE TRANSGENICOS
English translation by Ralph Miller

Soya planters in the State of Rio Grande do Sul, Brazil, are facing a problem: some weeds have become resistant to the glyphosate, the active principle most used in handling plantations.

The farmer, Guido Schneider, since 2002, plants soya in the Vacaria District in the State's mountain region. He had chosen this technology, he says, as it made handling easier. Mr. Schneider uses only one active principle for weed control: the glyphosate. It kills many plants, except GM soya, as the GM seed contains a gene that provides glyphosate resistance.

However, last December, when preparing the soil for sowing, Mr. Schneider met a problem. After the first treatment with the herbicide, he noticed that some weeds survived, in this case the buva (Baccharis erigeroides), a species native in RioGrande do Sul.

"We had problems with one and a half liters of glyphosate per hectare." He told us, "We noticed some patches in the field; we reapplied but even so there was no control. Then we had to change to another product."

At that time Globo Rural invited two researchers to visit Mr. Schneider's farm, the agronomists Leandro Vargas, from Embrapa (Brazilian Authority for Agricultural Research) and Mauro Rizzardi from the Passo Fundo University. Both verified, in the field, what was already known through research: some weeds were glyphosate resistant.

Although the major impact of the discovery is in the GM soy plantations, the problem first appeared in an orchard, also in Vacaria, in an apple exporting enterprise, with 1.5 million apple trees planted, where agronomist Cesar Orlandi noticed resistance for the first time. He told us that the company, for decades, uses glyphosate to kill weeds, mainly azevem (Lolium multiflorum), another grass native in Rio Grande do Sul. "In 2003, we began searching for information and help from EMBRAPA and research work was started in the area. It was discovered that azevem was, in fact, glyphosate resistant."

The material was taken to the Passo Fundo EMBRAP for analysis. In the laboratory several weeds were tested. The purpose was to establish if they were really resistant. Dr. Leandro explained the procedure: "Upon one of the plants the recommended dosage of glyphosate was twice applied. Onto another it was applied four times and onto a third eight times. Even when receiving the recommended dosage of glyphosate eight times the last plant survived and is going to produce seeds. On the on the hand, non resistant plants died with a smaller dosage of the herbicide, or with the recommend one. Resistance is natural; it will occur every time one excessively applies a product. This is what is happening with glyphosate, because it is being applied repeatedly over the same area onto the same plants. These possess a large number of genes, of which some are capable of giving herbicide resistance. There is no gene tranfer, the plant itself already has these genes they are simply expressed due to the repeated use of a herbicide."

According to EMBRAPA there are, nowadays about 10 different kinds of weeds in all the world, three of which are in Brazil, that don't die when submitted to glyphosate. The one that gives most problems is azevem, because this grass is cultivated in Rio Grande do Sul and sold to the soya farmers as mulch where the soya is going to be planted. The ground is not completely cleared, some of the grass is left to preserve the soil.

"The spreading of azevem occurs in two ways: one is through the windblown pollen that spreads over the whole area. The other that we have detected is through the seed business. The growers who produce azevem seeds sell these to other producers, who in turn end up, by unknowingly, introducing resistant azevem into their areas." Explained Leandro Vargas

Nearly a month later we again visited Mr. Schneider's farm and found the plantation well developed. The weeds were controlled with another product used with conventional soya, in addition to glyphosate. As a result costs were considerably higher than expected. We used a product which gave an additional cost of R$ 40,00 ( about US$ 19,00), per hectare."

"The farmer will have to make a cost/benefit analysis. The GM soya we have been planting up to now had a lower cost than this plantation with GM soya and herbicide resistant weeds. He will have to carefully weigh the cost of royalties and the cost of new herbicides and make the decision whether it is worthwhile, economically to continue planting GM soya, or take up, for a year or two, the use of conventional soya," pondered Passo Fundo University's agronomist Mauro Rizzardi. [Ralph Miller comment: "I don't see how this can be done considering the amount of GM seed remaining in the field after harvesting."]

Monsanto sent us a note on the subject. The company states that the resistance of weeds to glyphosate, or any other herbicide is a natural phenomenon. Monsanto also says that among herbicides, glyphosate is the active principle having the smallest number of herbicide resistant plants.



It wasn't supposed to turn out this way for glyphosate. For years, weed scientists said the risk of weeds developing full-blown resistance to the one-time burndown herbicide was relatively low.

That thinking has been drastically altered in recent years, however, as first glyphosate-resistant Italian ryegrass, then horseweed or marestail, then Palmer amaranth and now giant ragweed reared their ugly heads.

"...the number of glyphosate-resistant weeds tripled in just over eight years of repeated glyphosate use due to the introduction of Roundup Ready crops" - Steven Knezevic, integrated weed management specialist at UNL's Haskell Agricultural Laboratory http://www.lobbywatch.org/archive2.asp?arcid=7190

Glyphosate-resistant Palmer amaranth could be the biggest pest in cotton since the boll weevil and has the potential to damage the cotton industry, says a University of Ten

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