At the same time as he has been conducting tests with methyl bromide to satisfy Japan's quarantine requirements for cherries and apples, Dr. Hal Moffitt has been researching alternatives.
He began the quarantine work on apples in 1969, and on cherries three years later. What Japan required was a direct postharvest treatment to control the pests of concern, which on cherries are codling moth and cherry fruit fly, and on apples are lesser apple worm and codling moth.
Japan did not specify what the treatment should be, but Moffitt began testing methyl bromide fumigation, as the product had been used since the 1930s for insect control of fresh fruits, and was immediately available.
The Japanese government eventually accepted fumigation and cold treatment as a quarantine treatment. The first cherries were exported to Japan in 1978, and the first apples in 1995.
Moffitt also worked on other techniques that he believes could qualify as direct treatments, including irradiation, cold treatments, and low oxygen atmosphere.
The search for alternatives was stepped up when Dr. Lisa Neven joined the lab three years ago. Fumigation's negative effect on fruit quality was one of the main impetuses, although it was later announced that production of methyl bromide would be phased out because of its effect on the earth's ozone layer. Bruises on treated Rainier cherries tend to turn brown, and it causes some stem browning on all varieties.
"Our thinking has changed dramatically since we first started in '69," Moffitt said. "At that time, methyl bromide was the tool to use because it had been used on codling moth in the past, it was readily acceptable, and there was quite a bit of documentation."
Moffitt said Japan has specified only that it requires a direct treatment of some kind. He is optimistic that a nonchemical alternative treatment can be devised, although none is advanced enough to propose to the Japanese government yet.
Irradiation appears to be a very effective quarantine treatment for codling moth on apples, pears, and cherries, he said. Moffitt has worked with Dr. Stephen Drake, horticulturist with the U.S. Department of Agriculture in Wenatchee, Washington, and Battelle Northwest to determine the efficacy of the technique against the different stages of the insect and the impact on fruit quality. He said the U.S. Food and Drug Administration has approved a certain dosage of irradiation for treating fresh fruit, but public perception, which is beyond the scope of research, may be the greatest stumbling block.
Another drawback is that radiation does not kill the insect, but affects its development and makes it sterile. An inspector who found a live codling moth in a cherry would not know if it was sterile. He said researchers are working on markers that could show if an insect had been treated.
A heat treatment for cherries that Neven is working on also looks promising, he said, although producers are wary of any treatment that involves heating the fruit.
Moffitt said Japan will not accept a systems approach even though scientists have demonstrated that codling moth can be kept out of fruit without a direct postharvest treatment.
A systems approach involves a whole series of precautions, from pest control in the orchard, to sorting out culls in the orchard and at the packing house, and final inspection of packed fruit.
"We've done quite a bit of work over the years, working with the fruit industry, the state Department of Agriculture, and WSU [Washington State University] to document what's actually found on harvested fruit in the packed box, and we have found we can provide a degree of quarantine security equal to or greater than fumigation with methyl bromide," he said. "The assumption with the direct treatment is that every fruit's infested, and you have to kill that insect in every fruit."
In the last 17 years, millions of 20-pound boxes of cherries have been shipped to Japan, and inspectors have found only about ten infested cherries--all of them killed by the treatment.
Though the information he helped to compile on the efficacy of the systems approach did nothing to persuade the Japanese government to change its requirements, it has been useful in convincing other countries that a treatment is not required.
For example, in 1991, Mexico halted imports of U.S. cherries because of phytosanitary concerns. Mexico insisted the cherries should be fumigated, and the matter was referred last year to the Sanitary and Phytosanitary Committee of the North American Free Trade Agreement.
Moffitt was the U.S. representative on an international Expert Working Group, along with representatives from Mexico, Canada, and Europe, that met to consider the matter and make a recommendation to the Sanitary and Phytosanitary Committee. Moffitt said information he helped to develop on the systems approach played a very great role in precluding Mexico from imposing a quarantine treatment on U.S. cherries.
If the Mexican government approves a work plan proposed by the U.S. government, Pacific Northwest producers will be able to ship cherries to Mexico this season
