July 11, 2005, Capital Press Agriculture Weekly (US)

Aldicarb: Exposures exceed levels of concern for endangered species

FRESNO — California cotton growers, who use the systemic pesticide aldicarb at planting to rebuff insects such as thrips, relied on it especially this season due to rain and other trying planting conditions, a University of California cotton expert said.

“A lot of people were planting late, and it was a high thrip year,” said Dan Munk, a county extension agent based in Fresno County.

Aldicarb, sold under the brand name Temik, has been around for more than 30 years. In 2003, growers in the state applied 251,814 pounds of the product, according to a California Department of Pesticide Regulation report. Most of it went on cotton crops in Fresno and Kings counties, reports show.

However, lingering questions over negative environmental consequences to birds and other wildlife continue to dog the product nationally. On June 22, the Environmental Protection Agency said that part of its review of the pesticide, “estimated acute exposures based on both average and maximum application rates from aldicarb use on all crops assessed exceed levels of concern for endangered species and non-listed terrestrial organisms. Aldicarb shows very high acute oral toxicity to birds.” The EPA also announced a comment period which ends Aug. 22. It said it planned to release a human health risk assessment later this summer.

A spokesman for Bayer CropScience told the EPA that it objected to the preliminary findings, contending they were based on “artificially inflated hazard indices.”
“Recorded incidents have almost always been due to misuse or improper application,” Larry Hodges of Bayer told EPA in written comments. He also said, “There have been few documented incidents of field kills or wild birds or mammals in the United States associated with the use of Temik.”

Aldicarb is a restricted use systemic insecticide, acaricide, and nematicide. It is registered for use on citrus, cotton, dry beans, grain sorghum, peanuts, pecans, potatoes, soybeans, sugar beets, sugar cane, sweet potatoes, seed alfalfa, field grown ornamentals, and tobacco, as well as coffee and yams grown in Puerto Rico.

Aldicarb is a member of the N-methyl carbamate class of pesticides, all of which share a common mechanism of toxicity, cholinesterase inhibition, which effects the nervous system, according to the EPA. The agency said it is evaluating the cumulative risk posed by this group of pesticides before making final reregistration eligibility decisions on individual N-methyl carbamates, such as aldicarb.

Munk, the extension agent, said Temik has not caused groundwater pollution problems in the arid West that have occurred elsewhere in the United States. Similarly, he said the product also suppresses lygus, another bug that attacks cotton, and protects the plant by being taken up by the root system and guarding the crop from the inside.

“Some of the other options might be over-the-yop sprays,” said Munk, asked to discuss possible alternatives. Those options may be less environmentally desirable because of possible collateral damage to beneficial insects, he said.

EPA has previously said that aldicarb is considered highly toxic to insects, including honey bees, and to earthworms. Aldicarb is also highly to very highly toxic to many freshwater, estuarine, and marine fish and invertebrates, the agency says. The state of California already has some restrictions on aldicarb use where potential water pollution is suspected.

The compound is a steady member of the Pesticide Action Network’s “Dirty Dozen” pesticide list. The San Francisco-based activist group has worked tirelessly to limit or eliminate the product’s registration, calling it “one of the most toxic pesticides ever manufactured.”

Nationally, about 4.8 million pounds of aldicarb active ingredient are used per year on 4.9 million acres, the EPA said. The top five crops are: cotton (2,200,000 pounds), peanuts (600,000 pounds), potatoes (400,000 pounds), oranges (400,000 pounds), and sugar beets (200,000 pounds). (Chip Power, California Staff Writer)