Imperial Valley Girds for Voracious Whitefly

The bugs that ate Imperial Valley last fall are back--once again chomping away at crops, attacking nearly everything that grows.

Agriculture experts say this year’s infestation of a virulent strain of sweet potato whitefly is even worse than last year, when losses in the Imperial Valley alone surpassed $120 million.

However, U.S. growers and pest-control experts say they are a year wiser, better equipped to fight off the flies and optimistic that damage this season actually will be less than last year.

If they are right, consumers will notice little effect from the whitefly, unlike last fall and winter, when shortages in winter melons and--for a short period--in lettuce and some winter vegetables resulted in wild swings in retail prices.

And while growers, distributors and retailers are all hoping to avoid last year’s disaster and price hikes, “it’s hard to predict in August what will happen in December, especially when you’re talking about such perishable items as produce,” said Jan DeLyser of the Fresh Produce Council, a Los Angeles-based trade group.

Last year, grocers developed alternative sources for supplies of melons and winter vegetables and could turn to those sources again this year if needed. And other California farmers are experimenting with crops, such as cantaloupes, lettuce and broccoli, normally grown in the Imperial Valley for winter harvest.

Farmers have long battled the whitefly, but this new strain--now called the B strain--of the sweet potato whitefly is resistant to most currently used pesticides. It swept into the hot growing regions of the Southwest last year and showed a particular fondness for the Imperial Valley and the cantaloupes grown there in the fall.

The flies attach to the leaves of plants and suck out the nutrients, sapping the plant’s growth or even killing it. They excrete honeydew, a sticky, sweet substance that in turn is fed upon by sooty mold--a fungus that blackens and weakens the plants.

A mild, cool spring helped reduce the populations of the whitefly and seemed to help keep the pest from spreading north to California’s fertile Central Valley. The whitefly “never really left. . . . Their reproductive cycle just slowed down in the cooler months,” said David Ritter, coordinator of the whitefly program for the Imperial County Agricultural Commission.

So far this season, growers in Mexico have been the hardest hit. The economic impact has been tremendous in Baja California, said Guillermo Sada, of that state’s agriculture department. Growers there are waiting to hear the outcome of a meeting Wednesday, at which Baja officials asked the Mexican government to declare the area a disaster and provide funds to the financially stricken farmers.

Whiteflies have infested all of the nearly 50,000 acres in Baja planted in cotton, Sada said. So far, nearly 2,500 acres have been plowed under, yields from the remaining crops are expected to be cut in half and damage is estimated at $10 million.

This comes on top of earlier losses: Baja’s farmers this year did not even attempt their usual planting of sesame seed, which last year was wiped out by the whitefly. “And we drastically reduced the amount of cantaloupes and watermelons,” Sada said. “There’s been no income, no work for farm workers.”

In the Imperial Valley, where years of infestation by pink bollworms have already driven many growers out of the cotton business, the yields from the remaining fields planted in cotton may actually improve this year despite the whitefly, said Robert E. Bedwell, manager of the Planters Ginning Co. in Westmorland, the only cotton gin still operating in Imperial County.

The growing season has been shortened to reduce the impact of the pests, and cultivation techniques combined with a fortuitous rain are also helping the state’s cotton growers there.

Researchers throughout the state and in Arizona, Texas and Mexico--where crops also have been attacked by the whitefly--have been arduously attempting to find solutions to the infestation, including searching for natural enemies of the whitefly. But such biological controls will take at least three to five years to develop.

Growers have been trying different chemical pesticides, approved conditionally for the emergency, but primarily have relied on a number of non-pesticide techniques to limit the whitefly damage.

After the spring melons were harvested, growers were asked to plow up their melon fields, destroying the vines and weeds around the fields that provide food for the pests. Farmers are being asked to keep these fields clean of plants and weeds until the next crop is planted.

Many U.S. farmers also have held back from planting crops that the whitefly decimated last year. In the growing region around Yuma, Ariz., which matches the Imperial Valley in climate, if not productivity, “we had very few fall melons, because (growers) are not going to plant one of the most desired” of the whitefly’s food sources, said Mark Wilcox, a cooperative extension agent with the University of Arizona’s agriculture and natural resources department.

Wilcox said there is a “slight delay in planting for fall vegetables. People are watching to see what’s going on.”

In the Imperial Valley, too, “growers are leery of going in with a lot of acreage” in host plants, said DeLyser of the Produce Council. “The whitefly had a devastating impact on Imperial Valley growers last year, and that’s a loss they just can’t incur year after year.”