Spurred by the public's heightened concern about pesticides, San Diego County agricultural officials are leaning on farmers and growers to curb their use.
With the support of state legislation that took effect this year, county agricultural officials are pushing the use of biological control: releasing beneficial insects that prey upon pests.
Farmers and growers who half-heartedly adopt or refuse to use such methods early to control a pest population risk having their requests for restricted pesticides rejected when their pest problem escalates, says David Kellum, the county entomologist who often helps assess whether such chemicals should be issued.
"We're taking a much tougher stand these days against the use of pesticides," Kellum said. "And we're going to get tougher."
The county's hard line, however, has infuriated a handful of farmers and growers who say they must watch helplessly as pests overrun their fields and their livelihood.
But most farmers and growers say they recognize the need for biological control and support it in concept. They complain, however, that they are being unfairly pressured by politicians and agricultural officials--who, they say, are reacting to the public's unjustified hysteria about pesticides--to hastily adopt biological control before it has been proven effective.
In some cases, farmers and growers say, simple changes in the weather--temperatures too cold or too hot--can kill the beneficial insect before it can attack the pest. Biological control, in many cases, also takes time, often two to three years, to produce results. Critics also say that the beneficial insect must be deployed in huge quantities to be effective--a problem because rearing some beneficial insects is often a tricky task that severely limits supply.
"Most farmers and growers understand the need for biological control, and they try to use it, but very few would want to be limited to it," says Judge Charles Froehlich Jr., who, besides serving on the 4th District Court of Appeal, owns 75 acres of avocado groves north of Escondido. "Because the nature of the method is that you cannot be assured that it will work.
"But, because the general public is hysterical about pesticides. . . . it's more religious (in fervor) than it is scientific," he says. "What you're seeing is the politicians are reacting to the demands of the public, and in turn they're pushing the agricultural officials, who are now pressuring us."
Froehlich, however, is not an opponent of biological control. He and his wife, Millicent, are one of the 10 county avocado growers who have been participating in a three-year experiment using parasitic wasps to combat the omnivorous looper, a pest that ravages groves. Although county agricultural officials and participants call the experiment a success, it has not been a complete one.
A couple of years ago when Froehlich spotted the omnivorous looper in his groves, he followed county agricultural officials' instructions precisely: First, Froehlich released the parasitic wasps. Nothing happened. Then, he sprayed Dipel, a natural pesticide. The loopers multiplied. Soon, Froehlich's groves were infested with the pest. With no other means to turn to, a helpless Froehlich asked Kellum, the county entomologist, for the restricted pesticide Lannate. Kellum granted the request.
The entomologist insists that county agricultural officials are not trying to punish farmers or growers but instead want them to try safer pest-control methods that do work--most of the time. If the growers properly use such methods but are unsuccessful, Kellum says, they will be allowed to use restricted pesticides.
But agricultural officials warn farmers and growers that the days of pesticides are numbered.
"Farmers believe that they have an inherent right to spray (pesticides). . . . 'This is my property, and I can do what I want,' " Kellum said. "When San Diego was still rural, and houses and farms were far apart from each other, maybe you could spray. But now, if you spray, you're spraying on your neighbor, his dog. . . . and now, you have to worry about migrant workers living in the fields."
County Agricultural Commissioner Kathleen Thuner says she also must take into account research that continues to uncover pesticides' negative side effects.
In fact, public concern about the dangers of pesticides, especially after the Alar scare, pushed state legislators into passing the Food Safety Act of 1989. The bill requires farmers and growers to report all pesticides they use, not just restricted ones, and provides research money to find other options, such as biological control.
And money spent on biological control will be money well spent, says Kellum, the county entomologist.
In an attempt to persuade farmers and growers to use biological control, Kellum quickly points to the success--albeit limited--of the county's jointly sponsored experiment with the University of California in employing the parasitic wasp to control the omnivorous looper.
According to Gary Bender, the county's farm adviser for tree crops, the looper can be the avocado growers' worst nightmare. As an inchworm, the looper devours avocado leaves and bites the fruit "just for the hell of it," Bender said.
Because avocado trees are planted upon steep hills, traditional means of fighting pests--spraying pesticides from rigs pulled by tractors--cannot be used against the looper. The only alternative available, helicopter spraying, receives a lukewarm reception from growers because it is expensive and less accurate.
So county agricultural officials began an experiment three years ago using parasitic wasps to eradicate the looper.
The growers set up traps, baited with pheromone, a female sex hormone, to attract male omnivorous looper moths. When the traps fill with moths, growers are alerted to the loopers' mating season, a dangerous time for growers because it is when the female moth settles on an avocado leaf and lays eggs.
The growers then set out about 200,000 parasitic wasp eggs per acre. Once the eggs hatch, the parasitic wasp immediately seeks out the omnivorous looper egg and lays its egg inside the looper's egg. When the wasp hatches, the larvae wasp feeds on the looper egg's nutrients and kills the looper.
In the county experiment the parasitic wasp eliminated 50% of the looper population, making it nearly three times as effective as the commonly used Dipel, a non-restricted pesticide that killed only 19% of the looper population.
Although the restricted pesticide Lannate is even more potent--it eradicates from 90% to 95% of the pest population--it also kills many beneficial insects naturally found in groves, such as spiders that prey on the looper.
"When you eliminate the natural beneficials as well that's when you really open yourself up for a big problem," Bender said. "It's an invitation for the loopers to come roaring back."
But growers say achieving success with biological control is not easy.
For example, Froehlich explains, the timing of the release of the parasitic wasp eggs is critical to success because the wasps only seek and destroy the omnivorous looper eggs; the parasite does not attack the looper when it is a worm or a moth.
And Bender acknowledges that the program requires growers to learn to live with a certain number of loopers year-round.
"You can't kill all the loopers," he said. "If you do, then the parasitic wasps have nothing to feed on, and they'll die off."
And, sometimes, growers say, they just can't afford to wait for the parasitic wasp to do its thing.
"Sometimes, you have to use pesticides, or the only option you'll have is to go out of business," said Rick Opel, farm manager for Henry Avocado Packing Corp. in Escondido., a management, packing and sales company that manages about 2,000 acres of avocado groves throughout North County and parts of Riverside County. Opel also participated in the county experiment and estimates that he releaed at least 80 million parasitic wasps in 1989.
Although the wasp has demonstrated some effectiveness in combatting the omnivorous looper, farmers complain that it cannot be used against other pests. In fact, beneficial insects are very specific as to the type of prey they will attack; often they will only devour one type.
Although biological control has its faults, an increasing number of farmers and growers are experimenting with the method, says Jake Blehm, vice president of marketing for Ventura-based Rincon-Vitova Insectaries, the largest insectary in the United States.
Since 1985, the company's production of parasitic wasps (four different species) during the peak production period has more than doubled, to 100 million daily.
"Biological control is not the panacea, but there are lot more uses than we previously thought possible," said Blehm, whose company markets about a dozen types of beneficial insects.
Commissioner Thuner says she realizes that farmers and growers will not be persuaded overnight to give up pesticides. But she hopes that research will produce alternatives that satisfy growers and consumers alike. Some progress has already been made, she says.
"When I was hired in 1970 in Alameda County as an agricultural inspector, we were still using DDT," Thuner said. "Hopefully, by the time I retire, pesticides will be a thing of the past."