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State Initiates Review of Research Application for Use of Genetically Engineered Mosquitoes in Tulare County to Reduce Mosquito Populations – Oxitec voluntarily withdraws research application as of May 2023

In May 2023, Oxitec voluntarily withdrew its research authorization application to test the use of genetically engineered mosquitoes in California. DPR did not issue a decision on the application. More information on the research authorization previously submitted by Oxitec to DPR is available on DPR’s Research Authorization website.

Leia Bailey, Director of Communications
916-445-3974 |
April 5, 2022

En Español

SACRAMENTO - The California Department of Pesticide Regulation (DPR) has initiated the review of a research authorization requested by Oxitec, Ltd to release and study the use of genetically engineered Aedes aegypti mosquitoes to reduce the current Aedes aegypti mosquito population in Tulare County, California. DPR’s review of the research authorization application will entail a rigorous scientific evaluation, consultation with government agencies and consideration of public comments and input. DPR anticipates that the evaluation and review process will take at least several months.

The department opened a 15-day public comment period beginning April 5 and ending on April 19 at 5 p.m. to collect information and feedback from the public to be considered as part of the review and evaluation process for the application. Comments will be accepted via email at

DPR must approve a research authorization application before an unregistered pesticide can be field tested in the state. DPR toxicologists, entomologists, microbiologists, ecotoxicologists, and other department scientists will review the application, research design, scientific studies, and additional information.

Research authorizations are approved or refused based on an evaluation of whether that research may involve a hazard to handlers or field workers, public health, or the environment. Approved research authorizations limit both the area and the time period that the product may be tested and may include strict requirements or limitations on use, as well as monitoring and reporting requirements.

DPR’s evaluation of the research authorization application will include consultation with the California Department of Public Health, the County Agricultural Commissioner’s Office, the Delta Mosquito and Vector Control District and other appropriate government and local agencies.

Oxitec’s research authorization application proposes conducting field studies in Tulare County, California. The application submitted by the company proposes to release 5,000-30,000 mosquitoes per week at multiple study sites located within the county. The company has not yet identified specific sites for the release—a requirement for DPR’s review of the research authorization application. The proposed locations of the release sites, number of sites necessary to conduct the requested research and the number of mosquitoes released per site will be evaluated by DPR as part of its review of the application.

The department has posted on its website the following documents submitted by Oxitec as part of its research authorization application:

  • Application for research authorization from Oxitec, Ltd
  • U.S. EPA documents submitted to DPR by Oxitec related to its research authorization application

These materials and more information about the application request and DPR’s review process can be found on the department’s website.


The California Department of Pesticide Regulation’s mission is to protect human health and the environment by fostering safer and sustainable pest management practices and operating a robust regulatory system to monitor and regulate the sale and use of pesticides across the state.

DPR’s work includes conducting scientific evaluations of pesticides to assess and mitigate potential harm to human health or the environment prior to and following registration, registering all pesticides prior to sale or use in California, monitoring for pesticides in the air and water, and enforcing pesticide laws and regulations in coordination with 55 County Agricultural Commissioners and their 400 field inspectors. DPR invests in innovative research, outreach, and education to encourage the development and adoption of integrated pest management tools and practices and conducts outreach to ensure pesticide workers, farmworkers and local communities have access to pesticide safety information. More information about DPR.


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