Fruit fly eradication has been all but aban–doned in Hawai’i in favor of post-harvest commodity treatments – irradiation, in particular. This is despite the demonstrated technological feasibility of eradication in Okinawa, California, and Florida.
As late as 1993, members of the Hawai’i Fruit Fly Committee still embraced eradi–cation as an attainable goal in the state. For example, the HFFC’s Mike Kido reported in July 1993 to the HFFC executive commit–tee that: Based on previous large-scale USDA experiments, and the success in Okinawa, California and Florida, it ap–peared that the technology for eradication of both incipient and established fly popu–lations is currently available. The only major hurdles to a Hawai’i eradication pro–gram are registration of the chemicals and answering the pertinent environmental questions.”
Now, however, irradiation has been adopted as the state’s bright new hope for overcoming quarantine. Although eradication may be technically feasible, Kido told Environment Hawai’i, “With the DOA, UH and the USDA, you get all this bureau–cracy. They think themselves out of it and tie themselves into knots. That’s why they’re into post-harvest treatments. They wanted something successful because the rest was such a disaster.”
The focus on irradiation is short-sighted, Kido went on to say, noting that, “in order to have marketable fruit, you need to have control in the field.”
While irradiation has broadened mar–keting possibilities for Hawai’i’s fruit, it isn’t a solution to all of Hawai’i’s produce problems. Irradiation sterilizes pests, but it does not kill them. Pristine areas where the fruits are shipped and sold may be spared from infestation, but without proper con–trol, female flies can still damage the fruit by stinging it or laying eggs in it.
A Happy Medium
A new approach to “controlling the field” has been recently proposed by the USDA Agriculture Research Service. Roger Vargas, the ARS entomologist who is conducting the work, describes the approach as “bridging the gap between eradication and com–modities treatment.” Others working with Vargas on the study, called “Integrated Pest Management (IPM) of Fruit Flies in Ha–waiian Fruits and Vegetables,” are Mary Purcell, research entomologist, USDA-ARS; Roy Cunningham, research entomologist, USDA-ARS; and Ron Mau, extension ento–mologist, UH Department of Entomology.
A brief description of the study suggests that because eradication programs have high environmental and economic costs, “emphasis should shift toward area-wide pest management control programs and away from eradication. Furthermore, in the ab–sence of eradication programs in Hawai’i, systems approaches using IPM methodolo–gies are the best approach to producing higher quality fruits for commodity treat–ments such as irradiation.”
“We will utilize technology developed by the lab for eradication and repackage it for a management approach,” says Vargas. “The cost of eradication was so high, people quickly looked in other directions; now they’re interested in commodity treatment. But the problem is that many people can’t grow fruit because of fruit fly attacks, so I came up with a management plan.
“It hasn’t been funded yet,” he contin–ues, “but the proposal is one of seven being considered. If it isn’t funded, the objectives will be pursued anyway because they make good sense.”
A Total Approach
“Integrated pest management is the utiliza–tion of environmentally sound techniques and methods to maintain the pest popula–tion at levels below those causing economic injury,” according to a description of the project.
The project includes a series of large-area management approaches.
First, it involves the release of fruit-fly parasites, such as wasps, into the environ–ment at key sites. This process is described technically as “augmentive biological con–trol releases of parasites.”
Second, there is the use of a bait spray that does not harm native species. Many bait sprays use malathion, which damages non-target species and sometimes allows incidences of secondary pest outbreaks. Xanthene dyes, which are less harmful to the environment, will be used instead. Be–cause xanthene dye is photoactive, insects die when exposed to the sunlight after in–gesting the bait. “This compound is used in lipstick and Pepto-Bismol,” Vargas says. “It’s a common coloring that has a low mammalian toxicity.”
Third, the project will use male annihi–lation lures. There is a group of plant-derived compounds, called male lures, that have a “magical effect” on fruit flies, according to Vargas. This technique uses a small trap and a bit of the lure on a cotton wick to attract and collect the insects. “Methyl eu–genol and cue lure are the two most excep–tional,” he says, although they have never been registered for use in Hawai’i. “They’re relatively non-toxic,” Vargas adds. “People in Asia eat plants laced with methyl eu–genol. The object [of this part of the program] would be to register or demonstrate the use of these lures in male annihilation.”
Fourth, the project will employ the ster–ile insect technique (SIT). This entails rais–ing millions of male fruit flies in the lab, exposing them to irradiation to sterilize them, and then releasing them into the target areas.
Fifth, and last, the project will use neem–based insecticides. “Neem-based insecti–cides exhibit low mammalian toxicity, are an effective control for many insect groups, and are compatible with the activities of many beneficial insects,” a project descrip–tion states.
According to Vargas, this approach “will allow for the expansion of citrus, mango, atemoya, and other tropical fruit” cultiva–tion. The project, if approved, will have a budget of $5 million for five years. Possible collaborators include the University of Hawai’i Cooperative Extension Service, the UH Entomology Department, the UH Con–servation Biology Program, the state De–partment of Agriculture, the Tropical Fruit Growers’ Association, and various fruit and vegetable growers.
Volume 7, Number 10 April 1997