Pest Fighters Aim Sights on Ash Whitefly

After apparently eradicating a Mediterranean fruit fly infestation near downtown Los Angeles, state and county agricultural officials turned their attention Tuesday to an even more formidable winged enemy--the ash whitefly.

Since its discovery last summer at a Van Nuys vegetable stand, the tiny ash whitefly has been reported in tens of thousands of ash and other trees through Los Angeles County, prompting scores of phone calls by anxious homeowners, officials said.

County officials on Tuesday received a shipment of brochures from the state Department of Food and Agriculture that tell what can be done about the ash whitefly--which, unfortunately, is not much.

Little Can Be Done

“At this point there is no cure,” said Bill Edwards, deputy to the Los Angeles County agricultural commissioner.

The ash whitefly, which attaches itself to the underside of leaves and can slowly suck the life out of trees by stripping them of foliage, has no natural enemies in Southern California and is almost impossible to kill without soaking the entire plant in insecticide, state officials said.

At an early stage of its life, the ash whitefly secretes a honeydew that causes black, sooty mold to form on trees. Thousands of the pin-head sized larvae can attach to leaves and spawn the tiny adult flies that swarm similar to gnats.

The ash whitefly, like the Medfly, preys on citrus, peach and other fruit trees, prompting fears that the insect could cause millions of dollars in damage to the state’s agriculture business.

But unlike the Medfly, the ash whitefly cannot be treated with aerial malathion sprayings. To rid a single tree of the whitefly would require as much malathion as is used to kill a whole acre of Medflies, officials said.

Mission to Europe

To combat the ash whitefly, state officials are sending an entomologist to France and Italy next month to capture the Encarsia, a smaller than pinhead-sized wasp that is the insect’s natural enemy.

If the hunt is successful, agricultural officials could release millions of the tiny wasps as early as winter, said Larry Bezark, a state pest management specialist. But it will probably be years before the wasps can significantly reduce the ash whitefly population because the ash whitefly has reached epidemic proportions, he said.

So far, ash whitefly infestations have also been found in San Diego, Riverside, Orange, San Bernardino and Ventura counties, state Dept. of Food and Agriculture spokeswoman Veda Federighi said.

“It’s an outbreak situation where you have a new pest in a new environment with no natural enemies so the population just explodes,” said Bezark, who is charged with returning the Encarsia from Europe.

Medfly Success

Meanwhile, Los Angeles County Agricultural Commissioner Leon Spaugy said the battle against the Medfly infestation appears to be successful.

None of the crop-destroying Medflies have been found by county inspectors since the aerial malathion spraying Thursday over a 14-square-mile area north of downtown Los Angeles, Spaugy said.

“We haven’t picked up any new wild flies,” Spaugy said. “This is kind of a barometer that the aerial applications were effective.”

County officials expect to receive a shipment of 40 million sterile Medflies on Thursday for release Aug. 21. The sterile Medflies, which are expected to mate with the maturing larvae of wild Medflies now in the ground, will be released weekly inside a sector that includes Echo Park, Silver Lake and Elysian Park.

Los Angeles Department of Water and Power officials said Tuesday that laboratory tests over the weekend found no traces of the insecticide malathion in any of four reservoirs that are within the area sprayed by helicopters last week.

Those reservoirs, of which Silver Lake is the the largest, hold about 945 million gallons of water used downtown and in South and South-central Los Angeles.