As California Agonizes, Others Live With Medfly

While California debates how best to attack a stubborn infestation of the Mediterranean fruit fly, the option of eradication already has bypassed this tropical state and most other agricultural producing regions of the world, forcing farmers to find ways to coexist with the feared pest.

In Hawaii, Central America, Israel and elsewhere, the permanent establishment of the Medfly has not meant wholesale destruction of farming. And in some cases, agriculture actually has prospered alongside the pest. At the same time, the pest has brought hardships for both farmers and consumers: increased, regular applications of pesticides, marketing difficulties that can both raise prices and trim profits, and the everyday presence of worms in certain home-grown fruits.

On these tropical islands, the Medfly is cited as one of several reasons for agriculture’s failure to diversify into crops other than pineapple and sugar cane, which are not susceptible to the fruit flies. Residents also lament the difficulty of growing soft fruits without pesticide.

Oki Matsuura, 69, who was born and reared on this largest of the Hawaiian islands, remembers going into the highlands as a boy to gather wild fruit: mangoes, mountain apple and guava. “Oh, it was so sweet and delicious,” he recalled, smiling at the memory. Now the fruit is so wormy that Matsuura no longer bothers to pick it.

The experience of Hawaii and other Medfly-plagued regions might prove valuable to California. Some scientists believe that California must begin to learn how to live with the pest: Not only have new infestations occurred regularly over the last decade, but the public seems to be growing weary of the pesticide spraying programs that have been needed to eradicate the pest.

When it comes to California farming, comparisons to other regions can be tricky. There is no infested nation with agriculture as large or as varied as that of California, which produces more than half the nation’s fresh fruit and vegetables. Officials of the California Department of Food and Agriculture and the U.S. Department of Agriculture have warned of devastation to agriculture and serious economic ramifications should the pest become established in the state.

Nonetheless, the experiences of other infested regions suggest that the dire predictions might be overstated.

In Central America, for example, the Medfly is merely one of many problems, and not the worst, facing agriculture, concluded a 1977 study of the pest’s impact there by university scientists and officials of the U.S. Department of Agriculture. Coffee, grown in many Central-American countries, is a prime Medfly target, but coffee beans are largely unaffected by the pest because it infests the blossom rather than the bean itself.

“While this ubiquitous insect has a bad reputation and occurs in over 90 countries, people have learned to live with it,” the team of researchers said in their report. “Some of these countries export fruit with prescribed treatments to the United States.

“Perhaps the villain’s reputation has been both overstated and overrated.”

The experience of Israel, too, can offer some reassurance. A centrally run aerial pesticide spraying program has minimized damage to citrus and stone fruits such as peaches and plums. Fortunately for Israel, its major export market, Europe, does not require post-harvest treatment to guarantee pest-free fruit because the Medfly already exists on the continent.

“We have been living with the Medfly since the beginning of the century, and we have agriculture,” said Yoram Roessler, chief of Citrus Agro-Technical Services, a subsidiary of the Citrus Marketing Board of Israel. “It’s just another pest, a very serious pest, but it’s controlled to the level that we have almost no infested fruit in the market.”

Israel exports citrus, a Medfly host, to the United States and Japan, as well as to Europe. To meet U.S. quarantine requirements, the fruit is subjected to cold temperatures during shipping. Roessler estimates that the Medfly increases citrus growers’ costs by about 2%.

Israel’s citrus orchards are treated an average of six times a year with a malathion bait spray, he said, while stone fruits are sprayed as many as eight times. He added that virtually “nothing” is lost in yields in sprayed orchards.

“We control it quite nicely, but it’s still a pain in the neck,” Roessler said.

The pesticide, he said, can be applied selectively to prevent destruction of natural pest control programs, which include the use of beneficial insects. “But of course there must be some disruption,” he added. “No question about that.”

Here in Hawaii, the experience of growers have been both problematic and promising. The Medfly was introduced here at the turn of the century and rapidly proliferated. But then another pest, the Oriental fruit fly, invaded in the mid-1940s and pushed the Medfly out of its niche and into higher elevations. Today the Oriental and the melon fly pose greater threats to agriculture than does the Medfly.

“Economically, the Medfly is not of immediate concern” because the other flies do most of the damage, said Po-Yung Lai, plant industry administrator for the Hawaii Department of Agriculture.

In addition to population density and shipping and labor costs, the various fruit flies are blamed for this state’s need to import most of its produce.

“Of course you can adjust to anything. . ,” said Gene Gilmore, director of the USDA’s tropical fruit and vegetable research laboratory in Honolulu. “But run down and take a look at Safeway and some of the fruit prices.”

In an attempt to keep out the fruit flies, the U.S. mainland requires all susceptible commodities imported from infested regions either to be picked at certain times or to undergo post-harvest treatment or both. In some fruit, these requirements can diminish quality.

Because export-bound papayas must be picked hard and green, before the fly can lay its eggs in them, the fruit that leaves here is not as sweet or as flavorful as the papayas grown for domestic consumption. Moreover, the hot water treatment required for exporting papayas has driven up costs by at least 15%, according to a spokesman for a major tropical fruit company here.

Although papayas are an important export fruit, Hawaii’s soft fruits are more susceptible to the fly. Some residents complain that they typically lose half of their back-yard peaches to the pest.

“If you bite into a peach, you can expect maggots pretty much,” said Clark Hashimoto, a county agricultural extension agent on the island of Maui. “(The Medfly) loves peaches more than anything else.”

Unlike peaches, locally grown persimmons are sold in markets here. But malathion is not registered for use on the Hawaiian crop, and the Medfly will destroy as much as 25% of it before harvest, Hashimoto said.

Even when the fruit is not destroyed, growers must contend with embargoes imposed by importing nations that want to keep out the pest. Agricultural officials tend to agree that the Medfly’s most serious repercussion in Hawaii is not peach or persimmon losses, but the inability of the state to develop a potentially lucrative export market on the U.S. mainland for tropical fruit. There are no approved post-harvest treatments for many of them.

“The fruit fly isn’t the problem,” said farmer Eric Weinert, who grows such exotic fruits as star fruit, longan, lychee, rambutan, cherimoya and atemoya.

“I don’t spray anything. I harvest at the appropriate time, and I keep clean fields. If we could export, I think the fruit would be widely grown.”

Weinert, who grew up in Newport Beach and still shows his allegiances in the Los Angeles Laker T-shirt he wears, maintains that Hawaii’s climate is so ideal for tropical fruit that the state would have a strong advantage over other sellers. Export restrictions, however, have forced him to sell primarily to luxury hotels that cater to tourists hankering for a taste of the tropics.

Because of its pests, Hawaii is a hotbed of research into fruit flies, and some of this research may soon resolve Weinert’s export problems and also provide answers for California if it is forced to live with the Medfly.

In long, low buildings covered with metal roofs, researchers in Hilo inject various kinds of fruit with fly eggs and then try to kill off the pests inside by exposing the fruit to extreme temperatures or wrapping it in plastic to smother the insect. The challenge is to kill off the bugs without pesticide and without severely damaging the fruit.

John Armstrong, an entomologist with the USDA’s research service here, believes treatments that will enable growers to ship more tropical fruit to the mainland are only a few years away.

“Within the next two or three years, we will have developed a number of different quarantine treatments, hopefully for lychees, longan, rambutan and atemoya, “ Armstrong said.

Post-harvest treatments would be vital to California’s ability to export many types of fruit and vegetables should its farmlands become infested. According to the California Department of Food and Agriculture, which is managing the aerial spraying program in Southern California, the state’s Medfly-susceptible products would be barred from the nation’s warmer, fruit-growing states, including Florida, Georgia, Arizona and Texas, unless the commodities underwent USDA-approved treatments.

Most agricultural specialists said such a barrier would come down fairly quickly--in one to three years--because the best of measures would not be able to contain the infestation in California, and other states soon would be visited by the pests.

The longer-term challenge would be in treating products exported to nations such as Japan, which requires special treatments for commodities coming from infested regions. The United States and New Zealand are now the only major commodity exporters without fruit fly problems.

Developing adequate post-harvest treatments that would kill the pest and still protect the quality of California’s exports could be costly and take time. Treatment can damage some fruit and vegetables and reduce their shelf-life. Unlike farmers in most other nations, California growers might also face greater restrictions on pesticide use because of relatively stringent state environmental regulations.

Rather than switch to varieties of crops that would be less susceptible to the Medfly and less vulnerable to the effects of post-harvest treatments, California growers are looking to Hawaii for the weapons they believe will head off the much-dreaded infestation of California farmlands: sterile Medflies and Medfly parasites.

On the island of Oahu, the California Department of Food and Agriculture pulled former USDA entomologist Nori Tanaka out of retirement in 1982 to produce sterile Medflies. Sterile flies have been effective in eradicating relatively small Medfly infestations with only minimal pesticide spraying.

Tanaka, who is widely praised for his “green thumb with flies,” breeds 100 million of the insects a week in a cluster of ramshackle buildings in an industrial park in Honolulu. The flies’ sexual “perfume” and the decomposing protein the flies are fed permeate the buildings--and even the parking lot--with an overpowering, nauseating stench of rot that clings to clothing after only minutes and causes some visitors to faint. Radiation is used to sterilize the flies.

Despite Tanaka’s prideful ministerings, his warehouses are too small to produce enough flies to combat the current Southern California infestation. California agricultural officials are hoping that public opposition to aerial spraying will not halt the eradication effort before two new rearing laboratories on Oahu are put into full production, including a much larger, high-tech facility.

That lab, which looks like a palace next to Tanaka’s humble warehouse, opened last month and will be able to produce 500 million flies a week later this year.

In addition to sterile flies, parasites offer promise. In a recent demonstration project on the island of Maui, small wasps that are harmless to humans but deadly to Medfly larvae were credited with helping reduce twentyfold the population of an isolated pocket of Medflies.

Hawaii will soon embark on an even more ambitious demonstration project to eradicate the fruit flies with sterile insects from the island of Kauai. Public opposition has prevented aerial malathion spraying in Hawaii, and several skeptical scientists believe the state’s infestation is too entrenched ever to be eradicated from the islands, with or without spraying.

In the absence of much hope that the Medfly can be driven out, residents have resigned themselves to its vagaries. Tanaka, for example, says he regularly eats home-grown fruit.

“Oh yes,” he said, matter-of-factly. “Worms don’t bother me anymore.”