Sterile Mexflies Get a Warm Reception in Initial Release

Tuesday’s release of the first batch of sterile Mexican fruit flies in El Cajon went smoothly, despite a few extra deaths as some flies overheated in the high temperatures, state agriculture officials said.

The release, the second phase in the state’s effort to eradicate the citrus pest, took place from 7 a.m. to 5 p.m. throughout a 16-square-mile area.

Sixteen million sterile flies will be released from the backs of trucks Tuesdays through Fridays during the summer in the hope that they will mate with wild, fertile flies, producing eggs that don’t hatch.

Recent warm weather will slightly increase the mortality rate of the lab-raised flies but cause no damage to most of them, said John Hitchcock, a spokesman for the California Department of Food and Agriculture. The high in El Cajon on Tuesday was 105.

The flies hatch from pupae into adults in cardboard buckets, and some of the last flies to be released will die from overheating in the buckets, Hitchcock said.

Once in the wild, the flies establish their mating territories and escape the heat by finding the undersides of citrus leaves, where the shade keeps them cool, Hitchcock said.

More than 200 million Mexflies will be released in El Cajon this summer. The flies, which do not bite, ruin citrus by laying their eggs inside the fruit.