Experts See Whitefly as Peril to Fruit Crops

Since North America’s first ash whitefly was spotted in Van Nuys in July, the pest has spread into at least three other Southern California counties and could threaten deciduous fruit groves in the Central Valley if not checked by next summer, agriculture officials say.

“If it gets up there, the industry is going to become very, very interested,” predicted Bob Atkins, deputy Los Angeles County agriculture commissioner.

Agricultural specialists from several counties, universities and government agencies met on the problem two weeks ago and discussed the need for money to provide research as well as natural predators able to bring the whiteflies to a standstill.

So far, Atkins said Friday, “I have not heard of any agency saying, ‘Yes.’ ”

In the meantime, he reported, the flies are spreading unchecked because “there aren’t any natural ‘good guys’ out there.” He said the insect has spread “thoroughly” across Los Angeles County, has been reported in San Diego, Orange and San Bernardino counties and probably will travel further.

He said many callers, however, are actually seeing woolly whiteflies, “which with good pruning and control of ants doesn’t become much of a problem.”

The ash whitefly, which originated in the Mediterranean area, weakens trees by sucking sap from the undersides of leaves so that the leaves will drop off too early. It also secretes a sugary substance that draws ants and leads to formation of a mold that further harms trees.

Whiteflies are drawn to trees in the olive, rose and legume families, which include pear, apple, persimmon, peach, nectarine, apricot and plum trees.

“Pesticides don’t do a very good job,” Atkins said, “because the flies have a waxy coating that tends to repel the droplets. They are one of the most difficult pests on which to achieve satisfactory control.”

As for natural enemies that could bring the whitefly population down to manageable proportions, Atkins said a certain species of ladybug “will do a pretty good job,” as it does on aphids, and “some lacewings will feed on this type of insect.”

While waiting for some agency to offer funding for research and predators, Atkins said, officials hope the weather will buy them some time. “The cold will generally decrease the insect population,” he said. “The whiteflies are usually on deciduous trees and pretty soon they won’t have any leaves to sit on.”

However, he added, “If we don’t have some help by mid-summer, we’re going to have a repeat of this situation--if not worse.”