APHIS Expands Mexican Fruit Fly (Anastrepha ludens) Quarantine in San Diego County, California

FOR INFORMATION AND ACTION 
DA-2026-36 
September 23, 2026

Subject: APHIS Expands Mexican Fruit Fly (Anastrepha ludens) Quarantine in San Diego County, California 

To: State, Tribal, and Territory Agricultural Regulatory Officials

Effective immediately, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), in cooperation with the California Department of Food and Agriculture (CDFA), is expanding the La Mesa Mexican fruit fly (Anastrepha ludens; Mexfly) quarantine in San Diego County, California.

APHIS is taking this action to parallel the intrastate quarantine that CDFA implemented. On June 16, 2026, CDFA established a Mexfly quarantine in response to the June 4 detection of a wild mated female Mexfly from a trap in an avocado tree on a residential property in the city of Spring Valley, designated the Spring Valley quarantine. The quarantine encompassed approximately 76 square miles and contained 22.5 acres of commercial agriculture. On June 18, CDFA expanded the Spring Valley quarantine in response to the June 12 detection of one wild mated female from a trap in a grapefruit tree on a residential property in the city of El Cajon. The amended quarantine encompassed approximately 111 square miles and contained 338.5 acres of commercial agriculture that includes avocado, citrus, stone fruit, and tomatoes. On August 14, CDFA merged the La Mesa quarantine and the Spring Valley quarantine in response to the August 4 detection of a wild mated female Mexfly from a trap in a tangelo tree on a residential property in the city of La Mesa, designated the La Mesa quarantine. The La Mesa quarantine now encompasses 173 square miles and contains 338.5 acres of commercial agriculture that includes avocado, citrus, stone fruit, and tomatoes.

APHIS is applying safeguarding measures and restrictions on the interstate movement of regulated articles to prevent Mexfly from spreading to areas of the United States, as well as to prevent the entry of these fruit flies into foreign trade. This action is authorized by the Plant Protection Act (7 U.S.C. §§ 7701–7786) in accordance with 7 CFR 301.32 through 301.32-10. APHIS is working with CDFA to eradicate the transient Mexfly population following program guidelines for survey, treatment, and regulatory actions.

You can find maps and descriptions of all the current federal fruit fly quarantine areas on the APHIS Exotic Fruit Flies webpage. APHIS will also publish a notice about this change in the Federal Register.

For more information, contact: 

Catherine Marzolf 
National Policy Manager 
386-666-9932 
catherine.a.marzolf@usda.gov

/s/

Matthew A. Rhoads 
Deputy Administrator 
Plant Protection and Quarantine