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.