Informó por primera vez en 1998 en un par de huertos de almendros de California, la resistencia al glifosato se está extendiendo en los Estados Unidos y las malezas solo se están volviendo más inteligentes. El problema se ha intensificado a medida que múltiples especies de malezas ahora son resistentes en un número creciente de granjas, según un nuevo estudio extenso.
Kent Fraser, vicepresidente de la firma de investigación Stratus Agri-Marketing Inc., que realizó una encuesta a miles de productores estadounidenses en 31 estados durante tres años, dijo Farm Chemicals International, “We were surprised to see how quickly the problem of glyphosate resistant weeds has spread, especially in the Midwest. It is also alarming that the number of farms with more than one of the confirmed resistant species has increased so fast.”
The crop input industry has responded with products of differing modes of action designed for resistance management. The products are to be used as part of an integrated approach with crop rotation representing a key component. “It will be interesting to see if growers choose to rotate chemistries from year-to-year, mix it up with multiple modes of action at different application times in one year, or use products with multiple modes of action built in,” Fraser said.
U.S. growers told Stratus that 61.2 million acres of cropland are infested with glyphosate resistant weeds — almost double the number recorded in 2010.
Según el Estudio internacional de malezas resistentes a herbicidas, actualmente hay 396 casos únicos de resistencia a herbicidas a nivel mundial, con 210 especies. Se han reportado malezas resistentes a herbicidas en 63 cultivos en 61 países.
The survey’s results were dramatic:
- Casi la mitad (49%) de todos los productores estadounidenses dijeron que tenían malezas resistentes al glifosato en su granja en 2012, frente a 34% en 2011.
- Resistance is still worst in the South. For example, 92% of growers in Georgia said they have glyphosate-resistant weeds.
- The mid-South and Midwest states are catching up. From 2011 to 2012 the acres with resistance almost doubled in Nebraska, Iowa and Indiana.
- It’s spreading at a faster pace each year: total resistant acres increased by 25% in 2011 and 51% in 2012.
- The problem is getting more complicated. More and more farms have at least two resistant species on their farm. In 2010 that was just 12% of farms, but two years later 27% had more than one.
- Marestail (horseweed) was the weed most often reported with glyphosate resistance, followed by Palmer amaranth (pigweed). Another half-dozen species were tracked in the study.