Postharvest irradiation treatment for quarantine control of the invasive Drosophila suzukii (Diptera: Drosophilidae)

Authors: Follett, Peter; Swedman, Allison; PRICE, DONALD - University Of Hawaii

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2014
Publication Date: 6/2/2014
Citation: Follett, P.A., Janson, A.L., Price, D. 2014. Postharvest irradiation treatment for quarantine control of the invasive Drosophila suzukii (Diptera: Drosophilidae). Journal of Economic Entomology. 107(3):964-969.

Interpretive Summary: D. suzukii, an insect native to Asia, was trapped for the first time in California in 2008, and has since spread to many other states in the U.S. and to Europe. D. suzukii mainly infests stone fruits and small fruits and damage is caused by larvae feeding internally on the fruit pulp, and by the introduction of rot-type pathogens at the site of oviposition. Australia, New Zealand, and Mexico have imposed restrictions on the importation of strawberries, cherries, stone fruit, and table grapes from states with infested areas in the United States. Irradiation is a postharvest quarantine treatment option for exported commodities such as stone fruits and small fruits to prevent movement of this new invasive pest. Larvae (first, second and third instars) and pupae (1-2 days old, 3-5 days old and 7-8 days old) on diet were irradiated at target doses of 20, 30, 40, and 50 Gy in replicated factorial experiments and survival to the adult stage was recorded. The late stage pupa was the most radiation tolerant stage that occurs in fruit, and individuals irradiated at this stage readily emerged as adults; therefore prevention of F1 adults was the desired treatment response for large-scale validation tests with naturally infested fruit. In large-scale tests, a radiation dose of 80 Gy applied to late stage pupae in sweet cherries or grapes resulted in no production of F1 adults in >33,000 treated individuals, which meets the zero tolerance requirement for market access. A radiation dose of 80 Gy is recommended and will provide a margin of safety for quarantine control.

Technical Abstract: Irradiation is a postharvest quarantine treatment option for exported commodities such as stone fruits and small fruits to prevent movement of the new invasive pest spotted wing drosophila, Drosophila suzukii (Walker) (Diptera: Drosophilidae). The effects of irradiation on egg, larval, and pupal development, and adult reproduction in D. suzukii were examined. Larvae (first, second and third instars) and pupae(1-2 days old, 3-5 days old and 7-8 days old) on diet were irradiated at target doses of 20, 30, 40 and 50 Gy in replicated factorial experiments and survival to the adult stage was recorded. Tolerance to radiation increased with increasing age and developmental stage. A radiation dose of 40 Gy applied to eggs and larvae prevented adult emergence. Males and females were equally susceptible. The late stage pupa was the most radiation tolerant stage that occurs in fruit, and individuals irradiated at this stage readily emerged as adults; therefore prevention of F1 adults was the desired treatment response for large-scale validation tests with naturally infested fruit. In large-scale tests, a radiation dose of 80 Gy applied to late stage pupae in sweet cherries or grapes resulted in no production of F1 adults in >33,000 treated individuals, which meets the zero tolerance requirement for market access. A radiation dose of 80 Gy is recommended and will provide a margin of safety for quarantine control.