Entomology and pest experts have voiced concern that a mid-November decision by a federal court to reject the U.S. Environmental Protection Agency’s approval for the insecticide Transform will soon leave grain sorghum crops vulnerable to sugarcane aphids if the insects develop resistance to the only other insecticide currently labeled for the job.
On Thursday, Nov. 12, the EPA issued a cancellation order for all previously-registered products associated with the Dow AgroSciences technology Sulfloxaflor, including the pesticide marketed under the name Transform.
According to the cancellation order, the action was the result of a ruling by the Ninth Circuit Court of Appeals in a suit brought by the Pollinator Stewardship Council in 2013, which alleged that there was not sufficient evidence that the pesticide would not significantly harm bee populations.
Gus Lorenz, extension entomologist for the University of Arkansas System Division of Agriculture, said Transform is one of only two modes of action authorized for use that have been effective in controlling sugarcane aphids in grain sorghum.
“This is a bad situation for us,” Lorenz said. He said the only other product currently labeled for sugarcane aphids in grain sorghum is flupyradifurone, a pesticide produced by Bayer under the name Sivanto. “Not having an alternative chemistry is going to put a lot of pressure on Sivanto in 2016.”
Transform has been used to effectively control tarnished plant bugs in cotton in Arkansas for a number of years, it was adopted for use in grain sorghum under a temporary emergency measure, known as a Section 18, from the Arkansas Plant Board, in 2010, and again in 2011. The board later granted full approval for Transform in the crop in 2012. Now its use in both crops is in jeopardy.
Lorenz said reliance on a single mode of action to fight sugarcane aphids — especially in grain sorghum — is especially risky because the insect is prone to develop pesticide resistance very quickly.
“With aphids, the potential for insecticide resistance is huge, because they reproduce asexually,” Lorenz said. “They give birth to living young, they have a 3-5 day life cycle, so you can have 30-40 generations in a single year.
“Additionally, you’re talking about a bug that actually jumped hosts,” he said. “When the aphids left the sugarcane for grain sorghum, it left its natural enemy complex behind. So the natural control factors aren’t as good as they normally would be. We’ve had to rely heavily on insecticides for control.”
Grain sorghum is experiencing a boom in Arkansas production, with growers planting about 500,000 acres across the state, nearly tripling 2014 acreage. The crop experienced an approximately 25 percent increase in planting across the country, according to data from the U.S. Department of Agriculture.
Lorenz said the Division of Agriculture will apply for Section 18’s for the use of Transform in controlling both sugarcane aphids in grain sorghum and tarnished plant bugs in cotton for 2016. If the applications are denied, Lorenz said growers will need to use the modes of action available to them, possibly increasing the number of pesticide applications.
According to a press release from Dow Agrosciences, Sulfoxaflor has been used widely for four years with no demonstrable evidence of environmental harm, and the company is actively petitioning the EPA to renew registration for the technology.