Southern California grower-shippers are coping with a new quarantine and an expanded one aimed at protecting their crops from a pair of invasive pests.

Two Mediterranean fruit flies were discovered in a northern San Diego County trap Oct. 29. Another Medfly was trapped Nov. 1, according to a Nov. 18 news release from the California Department of Food and Agriculture.

The discoveries have resulted in a 79-square-mile quarantine. To eradicate the pest, the state agency began releasing 250,000 sterile Medflies per square mile per week Nov. 10 in an area surrounding the finds.

The Medfly discoveries came just days after a single Asian citrus psyllid was trapped in the area, which is about 45 miles from the border area where a psyllid infestation was discovered in August 2008. The newest psyllid find spurred the Department of Food and Agriculture to expand its psyllid quarantine area by nearly 1,000 square miles, the release said. It now covers portions of San Diego, Riverside and Imperial counties.

The quarantines were established just as the region’s 2009-10 citrus harvest is getting under way and within a few months of the start of the avocado harvest.