Pesticide use ramping up as GMO crop technology backfires-study

* Herbicide use 25 pct higher on biotech acres thannon-biotech acres

* Reductions seen in first several years, but now on rise * Super weeds and resistant pests drive more chemical use By Carey Gillam

Oct 1 (Reuters) - U.S. farmers are using more hazardouspesticides to fight weeds and insects due largely to heavyadoption of genetically modified crop technologies that aresparking a rise of "superweeds" and hard-to-kill insects,according to a newly released study.

Genetically engineered crops have led to an increase inoverall pesticide use, by 404 million pounds from the time theywere introduced in 1996 through 2011, according to the report byCharles Benbrook, a research professor at the Center forSustaining Agriculture and Natural Resources at Washington StateUniversity.

Of that total, herbicide use increased over the 16-yearperiod by 527 million pounds while insecticide use decreased by123 million pounds.

Benbrook's paper -- published in the peer-reviewed journalEnvironmental Sciences Europe over the weekend and announced onMonday -- undermines the value of both herbicide-tolerant cropsand insect-protected crops, which were aimed at making it easierfor farmers to kill weeds in their fields and protect crops fromharmful pests, said Benbrook.

Herbicide-tolerant crops were the first genetically modifiedcrops introduced to world, rolled out by Monsanto Co. in1996, first in "Roundup Ready" soybeans and then in corn, cottonand other crops. Roundup Ready crops are engineered throughtransgenic modification to tolerate dousings of Monsanto'sRoundup herbicide.

The crops were a hit with farmers who found they couldeasily kill weed populations without damaging their crops. Butin recent years, more than two dozen weed species have becomeresistant to Roundup's chief ingredient glyphosate, causingfarmers to use increasing amounts both of glyphosate and otherweedkilling chemicals to try to control the so-called"superweeds."

"Resistant weeds have become a major problem for manyfarmers reliant on GE crops, and are now driving up the volumeof herbicide needed each year by about 25 percent," Benbrooksaid.

Monsanto officials had no immediate comment.

"We're looking at this. Our experts haven't been able toaccess the supporting data as yet," said Monsanto spokesmanThomas Helscher.

Benbrook said the annual increase in the herbicides requiredto deal with tougher-to-control weeds on cropland planted togenetically modified crops has grown from 1.5 million pounds in1999 to about 90 million pounds in 2011.

Similarly, the introduction of "Bt" corn and cotton cropsengineered to be toxic to certain insects is triggering the riseof insects resistant to the crop toxin, according to Benbrook.

Insecticide use did drop substantially - 28 percent from1996 to 2011 - but is now on the rise, he said.

"The relatively recent emergence and spread of insectpopulations resistant to the Bt toxins expressed in Bt corn andcotton has started to increase insecticide use, and willcontinue to do so," he said.

Herbicide-tolerant and Bt-transgenic crops now dominate U.S.agriculture, accounting for about one in every two acres ofharvested cropland, and around 95 percent of soybean and cottonacres, and over 85 percent of corn acres.

"Things are getting worse, fast," said Benbrook in aninterview. "In order to deal with rapidly spreading resistantweeds, farmers are being forced to expand use of older,higher-risk herbicides. To stop corn and cotton insects fromdeveloping resistance to Bt, farmers planting Bt crops are beingasked to spray the insecticides that Bt corn and cotton weredesigned to displace."

(Reporting By Carey Gillam; Editing by Ken Wills)

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Keywords: USA STUDY/PESTICIDES