A series of court decisions and actions by the U.S. Environmental Protection Agency threatens to remove a popular Dow AgroSciences insecticide.
EPA recently proposed a ban of chlorpyrifos — the active ingredient (AI) in Dow AgroScience’s Lorsban, an organophosphate insecticide used for combating pests such as soybean aphids, spider mites and corn rootworm.
Entomologists contacted by DTN said it could take years before chlorpyrifos products are removed from the market. However, there is some concern that removing chlorpyrifos from the market could at some point complicate the battle against insects, especially when growers are being encouraged to rotate chemistry to guard against possible resistance.
For right now, however, when it comes to combating insects in soybeans, there are options.
According to EPA, corn accounts for chlorpyrifos’ largest agriculture market for total pounds used because overall corn acres are much larger than soybeans. However, in recent years use of chlorpyrifos has expanded in soybeans and has been on the decline in corn.
According to Dow AgroScience’s website chlorpyrifos use in soybeans expanded from about 200,000 acres in 2004 to some 8 million acres in 2008. Dow estimated chlorpyrifos was applied to about 11% of soybean acres planted in 2008.
Since 2000, Dow estimates soybean aphid infestations have caused economic yield losses of up to 45% in untreated fields. Soybean aphids are now present in 20 states including the Great Plains and into the Northeast and South, according to Dow.
The USDA estimates corn rootworm leads to more than $1 billion in lost revenue each year. That includes $800 million in yield loss and about $200 million in treatment costs.
Erin Hodgson, associate professor and extension entomologist at Iowa State University, said during a recent podcast there are many other options to combating insects in soybeans, making the potential loss of chlorpyrifos easier for farmers to overcome.
Christian H. Krupke, professor of entomology at Purdue University, said a look at Purdue’s 2015 insecticide recommendations shows there are plenty of options.
“Chlorpyrifos, while still in use, does not represent a large portion of the corn and soybean insecticide market,” he said. “While it was once thought to be indispensable, it has been largely replaced by a variety of pyrethroids for foliar sprays in corn and soybeans and by Bt for rootworm and some caterpillars in corn.
“Chlorpyrifos is one of the few remaining available compounds in the organophosphorus class of insecticides, which were at one time widely used and effective, but now have been replaced by other options both because of problems with resistance and their relatively high toxicity to mammals. I don’t anticipate a significant impact of the phase-out in these crops.”
Matthew E. O’Neal, Iowa State University entomologist, however, said when it comes to soybeans there should be some concern about what a chlorpyrifos ban could mean in years to come.
“My concern is if we get into a situation where we have a resistance to the other classes of insecticides used for aphids we’re going to need an alternative,” he said. “Chlorpyrifos is commonly used by farmers for aphids and other pests in soybeans. If one class of insecticide replaces its uses in soybeans, this could increase the likelihood of resistance occurring. In four or five years that’s when you’d start to notice there are is no chlorpyrifos and you’re looking for something that works.”
Dow AgroSciences suffered a separate blow last week when the EPA banned sulfoxaflor (Transform WG), also used to combat soybean aphids.
In June 2000 EPA eliminated all household uses except in ant and roach baits. According to EPA’s website termiticide uses were phased out as well. EPA also banned the use of chlorpyrifos products on tomatoes. In 2002, EPA restricted the use of chlorpyrifos on citrus and tree nuts, and other crops.
In 2012 EPA limited the use of chlorpyrifos by lowering pesticide application rates and creating no-spray buffer zones around public spaces, including recreational areas and homes.