The EPA has approved an increase of pesticide residue limits that is 300 times higher than the normal level to fight infestation from an insect that destroys rice sprouts.
Starting Oct. 7, a residue, or tolerance, increase for thiamethoxam will apply to rice and straw grown in Texas, according to a Federal Register notice.
The exemption to thiamethoxam is necessary to fight an infestation of rice delphacid, the EPA said. Rice delphacid is a leaf-hopping insect native to Central and South America.
Thiamethoxam is produced by the Swiss pesticide giant Syngenta AG and sold under the Cruiser and Endigo ZC brands.
The regular Environmental Protection Agency tolerance level for thiamethoxam on rice is .02 parts per million. The emergency exemption increases that level substantially, to 6 parts per million.
Part of Chemical Class
Thiamethoxam is a common insecticide that is part of a class of chemicals called neonicotinoids. In recent years, “neonics” have been the subject of intense criticism from environmental groups who point to the chemical’s impact on bees and birds.
The increased level is well above the acute exposure level. The EPA didn’t immediately respond to questions about why that level wouldn’t pose a human health risk.
As part of its evaluation of the emergency exemption application, the EPA assessed the potential risks presented by residues of thiamethoxam in or on rice and found they “would be consistent with the safety standard and with the Federal Food, Drug, and Cosmetic Act and with the Federal Insecticide Fungicide and Rodenticide Act [FIFRA],” according to the Federal Register notice.
Given the controversial history of neonicotinoids, a tolerance increase of this much was bound to raise eyebrows from watchdog groups.
“Increasing the allowable residues by that much is worrisome,” said Nathan Donley, a senior scientist at the Center for Biological Diversity.
“Even more worrisome is that rice fields are in standing water for much of the year,” Donley said. “It’s a crop that likes to grow in standing water. Given the propensity for neonics to persist and contaminate water bodies, this is very problematic.”
The EPA in March authorized a quarantine exemption under the FIFRA for the use of thiamethoxam on rice for control of rice delphacid in Texas.
The new time-limited tolerance for thiamethoxam will now expire on Dec. 31, 2024.
No insecticides are currently labeled specifically for this new pest, and the Texas Department of Agriculture says that products registered for leafhopper control in rice aren’t effective in controlling rice delphacid.
Rice delphacid first turned up in Texas in 2015, where it resulted rice sprout losses as high as 25%, according to the Texas agency. In October 2018, the state issued a crisis exemption for use of thiamethoxam on rice that expired nine days later. Due to the short time span, state officials say the pest wasn’t fully controlled.
The estimated drinking water concentrations of thiamethoxam for acute exposures in drinking water occurs at 0.02 parts per million for surface water and 0.063 parts per million for groundwater, according to the EPA’s Pesticides in Flooded Applications Model.
A request for comment from the U.S. Rice Producers Association was not returned.
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