Interim restrictions on the use of chlorpyrifos insecticide products may make it more difficult to control certain pests in crops including almonds.

Made a California restricted use pesticide two years ago, the latest restrictions on chlorpyrifos require application buffer zones up to 500 feet from identified sensitive sites. The required buffer zones will vary depending on the method of application and the amount applied.

These interim mitigation measures will be in place while the California Department of Pesticide Regulations, or CDPR and DPR, reviews comments and makes a final risk assessment for the chlorpyrifos.

DPR scientists believe chlorpyrifos, a broad-spectrum insecticide used for more than 50 years, may pose a public health risk as a potential toxic air contaminant based on the state agency’s assessments of the latest and controversial studies in the scientific community.

The interim rules are aimed at minimizing public exposure and the off-site movement of chlorpyrifos during applications, and reducing any runoff after application.

Sites that will require a buffer zone for applications include residential lawns, sidewalks, outdoor recreational areas, including school grounds, athletic fields, and parks; and all property associated with humans – occupied buildings.

Specific examples include homes, farmworker housing, other residential buildings, schools, daycare centers, nursing homes, and hospitals. Non-residential agricultural buildings, including barns, livestock facilities, and sheds, are not included in the prohibition.

This interim directive has been distributed to all county agriculture commissioners. Glenn Fankhauser, Kern County agricultural commissioner, said his inspectors will compare the interim rules with those existing in the county and then enforce the most restrictive.

Gabriele Ludwig, the Almond Board of California’s (ABC) director of sustainability and environmental affairs, said due to the proximity of the sites listed in many of the state’s almond production areas that the restrictions would curtail much of the chlorpyrifos use.

In a 2014 report by University of California Integrated Pest Management (IPM) and funded by CDPR, chlorpyrifos was found to have critical uses, that is uses with no or limited alternatives in four crops including alfalfa, almonds, cotton, and citrus.

For almonds, it was found to effectively control 12 insect pests; most notably leaffooted bugs and stink bugs. According to the report, there are no suitable alternatives to chlorpyrifos to control these insects and that the insecticide will remain an important pest management tool in almonds until new effective controls are registered or other management controls are developed.

The ABC’s research program has funded research for several years to better understand the leaffooted bug’s life cycle to develop an IPM system for it.

The UC IPM teams that created the CDPR report also pointed to the need for maximum residue levels established for all pesticides, given the importance of international trade for crops including almonds and citrus. Importing countries have established MRLs for chlorpyrifos, but may not for newer control chemistries.

Chlorpyrifos has been valuable for years when new invasive insect pests have shown up since it provided control until more targeted pest management strategies could be developed. It was the ‘go-to’ material for wine grape growers when they initially faced the vine mealybug.

“The loss of broad-spectrum insecticides, such as chlorpyrifos, will make it more difficult to respond to outbreaks of new insect pests,” Ludwig said. “Currently, UC IPM researchers have just documented the movement of the brown marmorated stinkbug, a relatively new pest to California, into Central Valley agriculture systems.”

Under the Irrigated Lands Regulatory Program, the detection rate of chlorpyrifos has declined significantly over the last 10 years - in many cases with no detections. The use of some formulations of chlorpyrifos (high VOC emitting formulations) is not permitted in California’s San Joaquin Valley during the summer to help reduce precursors to ozone (smog) formation.