FULLERTON : In World of Pests, It’s Bug Eat Bug

State health officials on Thursday took on a new pest, the white ash fly, but they have found a more natural way to kill it off than the noisy and controversial spraying used against the Mediterranean fruit fly.

Two vials of about 1,000 tiny, stingless wasps that naturally kill off the white ash fly were opened beneath a tree at the Fullerton Arboretum, starting off a process that officials hope will continue until the fly is eradicated.

The leaves of the tree were infested with the insects, which the Arboretum’s assistant director, Rico Montenegro, said “can cause some deformities on the growth of plant . . . as well as a general weakening of the plant.”

“There is some concern about agriculture,” he said. It’s not as severe as the Mediterranean fruit fly, but it is a problem.”

He said homeowners with fly-infested trees in their yards will notice a sticky, honeydew-like substance that drips to the ground.

Montenegro said white ash flies were first reported in the San Fernando Valley in 1988 and have since spread throughout Southern California, into parts of the San Joaquin Valley and Arizona. They are expected to eventually reach Oregon and Washington.

Tom Bellow, a UC Riverside associate professor of entomology, said newborn wasps eat the flies as they grow.

“These wasps . . . are about one-fiftieth of an inch long and they lay their eggs inside the immature white flies, and then (the young wasps) kill the white fly by eating it,” Bellows said. “After they’ve eaten the white fly, they hatch into another adult wasp and fly away to another tree and start the process over. These wasps will fly around naturally--attacking, killing and consuming the white fly.”

The wasps, which Montenegro said pose no danger to humans, will be released throughout Southern California all summer.