Less Irradiation Would Still Stop Fruit
By Jim De
April 15, 1997
Irradiation could become more
practical as a quarantine treatment to prevent fruit flies from spreading via
shipments of grapefruit and other produce, according to studies at the
Agricultural Research Service.
Irradiation--exposure to safe, very low levels of gamma ray
energy--interrupts the insects development. They cant reach
adulthood and produce offspring.
ARS scientists say it may be possible to reduce the irradiation amounts by
half or more. If further studies confirm this, irradiation could be done more
quickly and on fruits that can be damaged by the gamma ray doses now used.
Lowering the dose would make irradiation more feasible as an alternative to
fumigation by methyl bromide, a chemical scheduled to be phased out by 2001.
Irradiation takes only a few minutes and leaves no residue. The fruit or
other produce can be shipped immediately. And with a faster, cheaper treatment,
the fruit could arrive sooner at the supermarket--with more of its harvest
For two years, Hawaiian papayas and other tropical fruits have been approved
for shipping to the Chicago area. Exposure to 250 Grays (Gy) of gamma rays
ensures that no oriental or Mediterranean fruit flies that may be hidden inside
the fruit will survive to adulthood. But the irradiation amount needed to
obtain this exposure level could damage orange, mango, grape, avocado and other
fruits in a commercial shipment.
The ARS scientists found, however, that irradiation at only 16 Gy stopped
development of Mexican fruit flies in lab dishes. The studies used 100,000
Mexican fruit fly eggs, larvae and pupae. More recently, tests with a few
thousand grapefruit indicate 50 Gy may be adequate to halt Mexican fruit flies
hiding inside the fruit.
Scientific contact: Guy J. Hallman and Donald B. Thomas, USDA-ARS
Crop Quality and Fruit Insects
Research Unit, Subtropical Agricultural
Research Laboratory, Weslaco, Texas, phone (210) 565-2647, fax (210)
565-6652, email@example.com and