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Posted 7 April 09

Bayer releases list of adverse effects on imidacloprid

See this story also at: Department of Pesticide Regulation California

Asian citrus psyllid weapon re-evaluated
Action comes after Bayer CropScience releases list of adverse effects

Cecilia Parsons
Capital Press

Thursday, April 02, 2009

An important weapon in the citrus industry's fight to eradicate the Asian citrus psyllid is being re-evaluated by the state's department of pesticide regulation.

The agency has initiated a re-evaluation of 282 neonicotinoid products due to an adverse effects disclosure from the manufacturer, Bayer CropScience. At least one of those products is being used to treat the soil around sites where psyllids have been trapped in San Diego and Imperial counties.

The industry considers the psyllid a major threat due to its ability to carry the citrus greening disease that kills citrus trees.

The products can still be used and are under no additional restrictions as the re-evaluation continues.

The re-evaluation notice was posted on the Department of Pesticide Regulation website and DPR was accepting public comments until March 31. DPR spokesowman Lea Brooks said federal and state law require any new information about adverse effects be given to state regulators and U.S. Environmental Protection Agency.

The U.S. EPA confirmed it is conducting a similar re-evaluation of neonicotinoid pesticides.

Neonicotinoid pesticides have been registered for use on multiple crops in the U.S. since 1994. By 2006 there were 115 active registered products containing the neonicotinoid imidacloprid. The products include seed coatings, soil applications and foliar sprays.

A systemic insecticide, it does not kill on contact, but is taken up by the plants when applied through irrigation or on the soil. It kills targeted insects when they feed on the plant.

Brooks said the re-evaluation's goal is to determine the extent of the potential hazard and to identify ways to reduce or eliminate the problem.

The disclosure by North Carolina-based Bayer CropScience showed imidacloprid levels in leaves and blossoms varied depending on the application rate and type of plant, but the data indicated that residues in some plants measured above 4,000 parts per billion. Lethal concentration of imidacloprid needed to kill 50 percent of a test population of honeybees is 185 parts per billion.

Bayer CropScience data also indicated that when applied in the soil, imidacloprid residues remained relatively low for the first six months after application, but there was a dramatic increase that remained stable in some cases for more than 500 days after treatment. Brooks said studies by DPR showed treatment rates in the studies where high imidacloprid residue levels were found were similar to the rates on the labels for orchards.

Beekeepers nationwide and Bayer are aware of the re-evaluations, and their representatives are meeting to discuss the issue. Florida beekeeper David Mendes, who is vice president of American Beekeepers Federation, said there is ongoing dialogue with Bayer and the EPA on new ways to quantify material toxicity to honeybees.

Mendes is a member of National Honeybee Advisory Board, which has held meetings with Bayer. He said the current standards for measuring toxicity don't work well with the new formulations of pesticides. The goal, he said, is to find products that are safe for bees and have no long-term effects.

Many beekeepers think concentrations of the pesticide in pollen causes developmental problems in bee brood, Mendes told the Capital Press last year. He also conceded that much of the evidence against neonicotinoids is anecdotal. In California, some beekeepers have refused to place hives where they know the chemicals will be or have been applied.

Jack Boyne, director of communications for Bayer CropScience, said state and federal regulators routinely re-evaluate pesticides. California's re-evaluation was prompted in part, he said, on the concerns voiced by beekeepers and investigations into the cause of colony collapse disorder.

DPR spokeswoman Lea Brooks said state law requires the agency to continuously evaluate pesticides after they are in use. It also investigates when new information shows a pesticide may have caused, or is likely to cause, adverse effects on people or the environment.

Brooks said re-evaluation also gives the agency authority to ask for more studies and data when it has concerns about a pesticide.

Cecilia Parsons is a staff writer based in Ducor. E-mail: Cecilia Parsons


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