Arizona's cotton growers target invasive pest with new strategy
A joint initiative by cotton growers, the USDA and the University of Arizona's College of Agriculture and Life Sciences has used a combination of genetically engineered crops and the deliberate release of sterile pink bollworm to almost completely eradicate this invasive pest from the state's cotton crop and allowed Arizona's cotton growers to reduce their use of pesticides.
The pink bollworm (Pectinophora gossypiella) is one of the most destructive pests attacking the world's cotton crop. The female moth lays her eggs in the cotton's fruit capsule (it's boll). When the larvae hatch they eat through the whole boll. The damage they cause also allows other pests to infest the crop.
Originating in Asia it has been an invasive species in the USA since 1917. By the 1990s in Arizona the pink bollworm was so widespread that every other cotton boll was infested.
In 1996 Monsanto introduced Bt cotton, a genetically engineered crop containing a protein that killed pink bollworm, allowing a reduction in the use of insecticides.
However, in 2009, in response to poor cotton harvests in parts of India, Monsanto admitted that Bt cotton was no longer entirely resistant to pink bollworm in the region. In Arizona the UA team had already started developing their novel strategy to attempt to reduce resistance to Bt cotton in the pink bollworm population.
While the Bt cotton was successful against most pink bollworm a minority of the pink bollworm population developed a resistance to Bt cotton and was still able to feed on the crop. When they matured they mated with other resistant moths creating a new generation of Bt cotton resistant moths. This led to an explosion in the population of resistant pink bollworm.
The Arizona strategy involved rearing pink bollworm in the lab and sterilising them. During the moth's mating season the newly released sterile moths mated with the wild resistant moths.
''When a sterile moth mates with a fertile wild moth, the progeny won't be fertile,'' Bruce Tabashnik of UA's College of Agriculture and Life Science said. ''The sterile insects soak up the reproductive potential of the wild population. If you have a high enough ratio of sterile to wild moths, you can drive the reproduction of the wild population to zero.''
The Arizona strategy should provide a long-term solution to the pink bollworm problem, allowing a dramatic reduction in pesticide use.
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