County Mounts Chemical War on Oriental Fruit Fly

Reaching his arm through a hole cut in the truck’s window, Bill McCartney pointed a spray gun at a tree on a Monrovia sidewalk and fired.

The truck rolled on toward a utility pole, leaving a spritz the size of a dinner plate on the tree. The bait contained a scent that attracts the male Oriental fruit fly laced with an insecticide that will remain deadly for two weeks.

Two weeks ago, four flies were discovered on grapefruit, guava and orange trees within a square mile in Monrovia and Arcadia. If one more fly is trapped in the same area, a quarantine restricting the movement of home-grown produce could be imposed, Los Angeles County Agricultural Commissioner Leon Spaugy said in a recent statement.

Since Oct. 11, McCartney has been squirting trees--his arm protected from the mist by a plastic sleeve taped over his window--in the battle to eliminate the pest from the two cities. For at least another two months, more than 600 applications per square mile will be made every two weeks over a nine-square-mile area in Monrovia and neighboring Arcadia.

This is the second time the Oriental fruit fly has caused an infestation in the San Gabriel Valley, said entomologist Becky Jones of the state Department of Food and Agriculture.

A quarantine on 65 acres in and around West Covina was lifted earlier this month. About 70 square miles in the Silver Lake and Echo Park area is under quarantine after the discovery of five flies during routine inspection of traps in back yard fruit trees.

“This has been a very busy year for fruit fly infestations, particularly for the Oriental fruit fly,” Spaugy said. The pest has been detected in the county 12 times this year.

The aerial spraying of malathion used in Mediterranean fruit fly eradication is not necessary here because state and county bug specialists have found a more powerful weapon in “a tremendously attractive male lure,” said Bob Atkins, the county’s deputy agricultural commissioner in charge of pest prevention.

In the “male annihilation technique,” the enticing methyl eugenol is mixed with the pesticide Naled, which kills both on contact and upon ingestion.

If that seems like a lot of attention for a lowly insect, it is with good reason. The fly could cost the state $44 million to $176 million in pesticide expenses, crop losses and quarantine restrictions if it isn’t successfully eradicated.

Originally from Southeast Asia, the fly has become a major pest in Hawaii, since it was introduced in that state in the 1940s. One of the most harmful of all fruit flies, the species attacks more than 250 varieties of fruits and vegetables, including important California crops, such as citrus, avocados and grapes.

The fly is a notoriously strong flier that has traveled 30 miles in search of food and a place to lay eggs. As a result, infestations can spread quickly.

Slightly larger than a housefly, with a yellow-striped abdomen and yellowish legs, the Oriental fruit fly begins its 90-day life cycle in the pulp of a fruit or vegetable, after the female deposits 10 to 100 eggs under the skin of her target.

Maggots hatch and tunnel through the fruit for nourishment, turning their host into a rotten, mottled mass. Sometimes the fruit drops from the tree prematurely as a result, said state pest control specialist Roger Faulkner.

The larvae either drop from or crawl out of the fruit to burrow as far as an inch into the soil to continue developing. Adult flies emerge within 12 days.

Fly traps throughout the state are checked weekly all year, Faulkner said.

When a fly is caught, trapping is intensified and fruit in the area is inspected for the creamy-white larvae. Because there are so many varieties of flies, any maggots found are dropped into a vial of alcohol and mailed to Sacramento, so that state entomologists can confirm the identification. No larvae have been found in Arcadia or Monrovia, Faulkner said.

Fruit from infested countries must be fumigated before entering the state, but often untreated produce is carried in by mail or travelers. County, state and federal agricultural officials will be meeting later this month to discuss ways the pests are slipping into California and how to stop it, Spaugy said.

BACKGROUND * The discovery of four Oriental fruit flies in Monrovia and Arcadia earlier this month was the second time the flies have been found in the San Gabriel Valley this year. To eradicate the flies, officials are treating a nine-square-mile area. A quarantine imposed in July on 65 acres in and around West Covina was lifted last month.