The California Department of Pesticide Regulation is proposing to permanently allow 1,3-dichloropropene, or 1,3-D, fumigation of individual tree planting sites, with tighter limits on how many holes can be treated per acre. The proposal would provide for continued use after the current interim approval expires in September 2027.
DPR announced the proposal October 30 and opened a 45-day public comment period running through December 14, 2026. The announcement describes a proposed regulation, not an adopted rule or a new effective date.
Interim approval would become permanent
The department granted three-year interim approval for the tree-hole method in September 2024, following a request from the Tehama County Agricultural Commissioner. That approval provides the starting point for the permanent rules DPR now seeks.
DPR proposes retaining most provisions of the interim approval, including timing and setback requirements. It would also impose more stringent limits on the number of individual tree holes per acre that can receive 1,3-D treatment.
The proposal pairs those use restrictions with a reporting change: a specific field fumigation code for tree-hole applications. That would identify the method separately in use reporting under the updated 1,3-D application requirements.
For growers and applicators following the proposal, the key distinction is between continuing permission for the method and changing its conditions. DPR is proposing both: a permanent regulatory framework in place of the expiring interim approval, alongside tighter treatment limits and a dedicated reporting code.
Comments due December 14
DPR is accepting comments through its SmartComment online public comment portal, by email at dpr26006@cdpr.ca.gov, or by U.S. mail. The December 14 deadline is the public's opportunity to respond to the proposed changes before the department completes the rulemaking process.
