Inspectors have trapped a single light brown apple moth in a residential area of Napa, Calif. State and federal laboratories confirmed the identification of the pest.
The find marks the ninth county in which the pest from Down Under has been found.
In April, the U.S. Department of Agriculture quarantined eight California counties as well as the entire state of Hawaii because numerous traps have picked up the light brown apple moth.
Included in the quarantine are Santa Clara, San Mateo, Alameda, Santa Cruz, Monterey, Contra Costa, San Francisco and Marin counties. All are near San Francisco Bay in Northern California.
Since the initial trap catch on Feb. 27, inspectors had caught 1,632 moths as of May 1. The vast majority have been in Santa Cruz County.
All host materials, which include nursery plants, fruit and other plant material, must be visually inspected and certified free of the pest before leaving the quarantine zone.
The quarantine also requires extensive trapping, nursery plant treatments and precautionary production practices.
The USDA included Hawaii in the quarantine because the pest is known to be established in the state, but no data exists on the exact distribution of the pest. All individual shipments of host commodities leaving Hawaii must be visually inspected and certified as free of light brown apple moth before leaving the state.
A technical group composed of international experts on the moth will meet May 17 and 18 in San Jose to discuss the situation and make recommendations on how to curb the pest.
The small moth, which is native to Australia, has a host range of 250 plant species. It destroys, stunts or deforms young seedlings; spoils the appearance of ornamental plants; and injures deciduous tree-fruit crops, citrus and grapes.