Irradiation quarantine treatments for mango seed weevil and Cryptophlebia spp.
Follett P. A.
Author Affiliation: U.S. Department of Agriculture, Agricultural Research Service, Tropical Fruit, Vegetable and Ornamental, Crop Research Laboratory, U.S. Pacific Basin Agricultural Research Center, P.O. Box 4459, Hilo, HI 96720, USA.
International Atomic Energy Agency Technical Documents (IAEA-TECDOCs) : 9-18
Abstract : Irradiation was explored as a method to prevent adult emergence in, or to sterilize, mango seed weevil. Mixed-age mango seed weevils in mangoes were irradiated with target doses of 50, 100, or 300 Gy and held for adult emergence. The 300 Gy treatment (dose range 180-310 Gy) did not prevent adult emergence. Emerging adults from the 100 and 300 Gy treatments were lethargic and short-lived, and laid no eggs, indicating sterility. An irradiation quarantine treatment (300 Gy) to sterilize mango seed weevil in mangoes has been approved. This treatment opens US mainland markets to mango exports from Hawaii. Cryptophlebia illepida and C. ombrodelta (Lepidoptera: Tortricidae) are quarantine pests that attack lychee, longan, rambutan, mangoes and other fruits in Hawaii. Studies were undertaken to determine whether irradiation treatment at 250 Gy, an accepted treatment for disinfestation of fruit flies in tropical fruits from Hawaii, would also control the two Cryptophlebia species. C. illepida was determined to be more tolerant of irradiation than C. ombrodelta and so C. illepida was used in detailed tests. Using the criterion of success in developing to the adult stage, the pattern of tolerance to irradiation in C. illepida was generally eggs early instars late instars pupae. The most tolerant stage that could potentially occur in harvested fruits is the late (fourth and fifth) instar. No C. illepida larvae receiving an irradiation dose ?125 Gy and emerging as adults produced viable eggs, indicating sterility can be achieved at doses 250 Gy. Large-scale tests in which 11 256 late instars were irradiated with a target dose of 250 Gy resulted in a pupation rate of only 8.4% and no adult eclosion. Therefore, the irradiation quarantine treatment of a minimum absorbed dose of 250 Gy approved for Hawaii's fruit flies will effectively disinfest fruits of any Cryptophlebia in addition to fruit flies.