El Cajon Is Mexfly-Free Halfway Through Program, Officials Say

Midway through the eradication program, the battle against the Mexican fruit fly has succeeded in El Cajon and Compton, state agriculture officials said Tuesday.

No wild Mexflies have been discovered in El Cajon since May 5, when two egg-bearing females were trapped a quarter mile from the site where a male fly was trapped April 25, California Department of Food and Agriculture officials said.

Intensified trapping and inspection of fruit in the infested and quarantined zones have revealed no new wild adult flies, or eggs or larvae, which live inside citrus, said Jose Aguiar, an inspector with the state agency.

In Compton, the other Southern California community with Mexflies, the only wild fly discovered since a 14-square-mile infestation was declared this spring was an immature male trapped July 23 in a lemon tree in Watts, a quarter mile outside the treatment zone, officials said.

The one fly does not constitute a new infestation, but the area in which sterile Mexflies are being released was expanded to 16 square miles to include the area where the fly was trapped, said Larry Cooper, a Food and Agriculture spokesman.

The earlier trappings of the three wild flies in El Cajon constituted an infestation, or a “new breeding population,” according to state agriculture guidelines.

The trappings triggered the state’s controversial decision to spray malathion three times by helicopter, in May and June, followed by the continuing release of 16 million sterile flies per week in the 16-square-mile treatment area.

The release of sterile flies, designed to mate the wild flies out of existence, is at the midway point in El Cajon and Compton.

Part of last week’s shipment of sterilized pupae was lost in transit, but it will not affect the program and the sterile releases are proceeding as planned, said Martin Muschimske, an economic entomologist with Food and Agriculture.

“The purpose is to over-flood the wild population out there with a preponderance of sterile flies, so statistically we can be in the 100% probability that the flies cannot mate with fertile females,” Muschimske said.

Despite the massive number of sterile flies being released, a statistical “blind spot” keeps entomologists from knowing the exact chances that a fertile female will mate and lay eggs, Muschimske said.

The sterile releases began June 26 in El Cajon and are projected to last until Sept. 5. Compton’s schedule is a week ahead of El Cajon’s.

Those timetables, however, could be affected by variables such as higher-than-normal temperatures, which accelerates the flies’ rate of emergence from their underground pupae stage into adult flies, Aguiar said.

In El Cajon, more than 96 million sterile flies have been released. An estimated 180 million flies are to be released by the end of the summer.