Replacing pesticides with genetics - the new york times

Replacing Pesticides With Genetics - The New York Times Replacing Pesticides With Genetics Mating moths. Scientists hope to stop using pesticides to fight diamondback moths by geneticallyengineering them with DNA that kills female larvae. Credit Dan Olmstead/Cornell University GENEVA, N.Y. — Every spring, a host of unwelcome visitors descends on theHansen farm in upstate New York. Diamondback moths blown in from the Souththreaten rows of cabbages to be sold for slaw and sauerkraut.
The moths can't be fought off with a single insecticide. Workers must spray aseries of chemicals throughout the growing season to keep the moths' numbers incheck.
"You have to rotate what chemical you use so you don't get a buildup inresistance," said Ed Hansen Jr., whose family has farmed the land for nearly acentury. This adaptability, he said, makes the moths one of the worst pests to Replacing Pesticides With Genetics - The New York Times deal with each season.
At a university laboratory down the road, scientists are hoping to substitute sexfor sprays. They have genetically modified thousands of diamondback moths,infusing them with DNA designed to kill female larvae. In August, the researchersbegan introducing the altered moths into outdoor cages in a field, where theirmating habits will be monitored.
If the results are promising, the transgenic moths will be released into a smallcabbage patch next summer. It would be the first experimental release onAmerican soil of insects genetically engineered to self-destruct.
A plan to let similarhas met withstrong opposition amid fears about being bitten. But federal regulators seem tohave few worries about the safety of the moth experiments.
"Our goal as a community is to reduce the amount of pesticides used inagriculture," said Anthony Shelton, the entomologist running the experiments atthe Cornell University Agricultural Experiment Station. "Why not use genetics toaccomplish this?" the diamondback moth was once a minor nuisance. Itbecame an agricultural headache in the late 1940s as chemical pesticide useexploded. The moth, the first crop pest to evolve resistance to DDT, multiplied asfeebler competitors died off.
Today, the pest is found where kale, broccoli, Chinese cabbage and other cabbagecousins grow. Hungry caterpillars that hatch from eggs laid on the plants costfarmers an estimated $5 billion a year worldwide. And the diamondback mothcontinues to adapt to new generations of pesticides. In Malaysia, it is immune toall synthetic sprays.
In the 1990s, scientists searching for alternatives to pesticides bombardeddiamondback moths with gamma rays to sterilize them. This tactic had Replacing Pesticides With Genetics - The New York Times eradicated from the United States a parasitic fly larva called the screwworm; fordecades, hordes of radiation-sterilized male flies were released in the wild,outcompeting fertile males and reducing the population.
But the diamondback resisted even radiation. So Oxitec, the Britishbiotechnology company working with Dr. Shelton, found another way to sabotagediamondback reproduction. The company, an Oxford University spinoff, stitchedtogether scraps of DNA from a virus and a bacterium to make a gene deadly tofemale insects.
A female larva harboring the gene is dependent on regular feedings of theantibiotic tetracycline to survive. Out in the wild, she dies long before reachingadulthood.
In a studyin July, male moths carrying the gene wipedout communities of normal moths living in small cages. Females mating withtransgenic males had as many offspring as those coupling with unaltered males,but the female offspring died before being able to reproduce.
Only some of the male offspring inherited the synthetic gene, which tends todisappear after a few generations. So thinning the moth population requiredmultiple waves of assault by fresh males bred in the lab.
Dr. Shelton's outdoor cages, also stocked with wild moths, will test how well thegenetically engineered males compete in a bigger arena. The release next summerinto the field would take the technology one step closer to being used on farms.
The strategy has drawn criticism. Groups opposed to the use of geneticallymodified organisms worry that the protein made by the synthetic gene couldharm wildlife that eat the moths.
"We would argue that more information should be collected," said HelenWallace, the director of GeneWatch U.K.
Replacing Pesticides With Genetics - The New York Times Haydn Parry, the chief executive of Oxitec, says the company addressed thisconcern and others in data submitted to the Department of Agriculture.
"We fed the protein to mosquitoes, fish, beetles, spiders and parasitoids," he said.
"It's nontoxic." After weighing the evidence, the department decided the planned experimentswould have no significant effect on the environment.
A public letter signed in June by theNew York protested any outdoor trials. The association cautioned that escapingmoths could contaminate nearby farms and endanger their organic certification.
Yet studies suggest the likelihood of diamondback moths straying is low. Wildmoths released into the open tend to stay put as long as they have food andcompany. Any that do venture farther afield are likely to be wiped out by NewYork's cold winter.
Even if strays are found, legal experts say that national organic standardspenalize only the deliberate use of a genetically modified organism.
"If these moths came across into an organic field inadvertently, that would not bea problem for the farmer," said Susan Schneider, a professor who specializes inagriculture and food law at the University of Arkansas School of Law.
Insects that do wander into other fields can be identified by their red glow underultraviolet light — caused by another gene inserted into their DNA, this one fromcoral.
Even if the moths in Dr. Shelton's experiments pass muster, there is still noguarantee that farmers will use them.
"At the end of the day, the technology may not go forward for commercialreasons," said Mark Benedict, an entomologist at the Centers for Disease Control Replacing Pesticides With Genetics - The New York Times and Prevention.
Other weapons developed for combating diamondbacks — larva-eating wasps, forinstance — have struggled to compete with cheap chemical pesticides.
"What almost always happens is the pesticides take precedent," said MichaelFurlong, an entomologist at the University of Queensland. "The growers can'tresist spraying, as it's the easiest thing to do." As for Mr. Hansen, he says he has not ruled out using the genetically engineeredmoths one day in the continuing battle to save his cabbages.
"I'm glad they're doing these experiments," he said. "But it's really early days." Correction: September 3, 2015
A picture on Tuesday with an article about genetically modifying diamondbackmoths, a farm pest, with DNA designed to kill female larvae carried anincorrect credit. The photograph, of two mating moths, was taken by DanOlmstead of Cornell University; it was not provided by the Cornell Alliance forScience.


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