Chlorpyriphos (Lorsban) Must be Used More Carefully

By Patrick Cavanaugh, Deputy Editor

California Department of Pesticide Regulation (DPR) reports an important, broad-spectrum organophosphate insecticide known as Chlorpyriphos, or Lorsban, may be further restricted due to evidence of potential human health and environmental risks, presence (parts per billion) in some California waterways, and pressure from the EPA. Brian Leahy, director of the California Department of Pesticide Regulation, said, “Chlorpyriphos is an important tool and we know there are important times when you have to use it.”

Registered and widely used in agriculture across the nation for more than 40 years, DPR has made it a restricted-use material. Leahy said, “We are trying to work with the grower community to improve how they use it. We are also working with UC IPM to look at essential needs, but we know that as we look at Chlorpyriphos, we are going to have to put additional restrictions on it.”

“We simply need for it to stay on target, and not be getting into the human body. We are seeing that it is, and we are going to continue to make sure that people use it thoughtfully and wisely,” he said.

And Leahy is very confident that growers can use this material and keep it on target, “I have seen farms that use it only when they really need it, and that is what we want. We can’t lose this tool and we are going to keep it only by showing we can greatly reduce off-site movement to the human body and watersheds,” he noted.

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Resources:

According to the University of California Agriculture and Natural Resources 2014 Chlorpyrifos Report entitled, “Identifying and Managing Critical Uses of Chlorpyrifos Against Key Pests of Alfalfa, Almonds, Citrus and Cotton“:

Chlorpyrifos plays a critical role in many IPM programs for controlling pests that threaten the productivity and economic well-being of California producers and in maintaining the high quality standards required by consumers and international export markets. This active ingredient also allows production of animal feed to support the important dairy industry in California. For some pests, chlorpyrifos is one of the last effective organophosphate insecticides available and may provide an important alternative mode of action for insecticide rotations to prevent the development of resistance to newer insecticide products. For others, this product is one of very few products with international registrations with established maximum residue limits (MRLs) that allow unhampered trade. Chlorpyrifos may also be a key tool for controlling invasive pests as well as endemic pests occasionally found in extremely high population densities. 

The California Department of Pesticide Regulation reports that the combined use of chlorpyrifos in alfalfa, almonds, citrus, and cotton has decreased since 2006. 

Although newer insecticides are also available to manage some pests in these four crops, there is a continued need to preserve the availability of chlorpyrifos for specific situations.

“Assessing the Health Risk of Pesticides,” California Department of Pesticide Regulation