Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/15/2012
Publication Date: 12/5/2012
Citation: Follett, P.A., Snook, K. 2012. Irradiation for quarantine control of the invasive light brown apple moth, Epiphyas. Journal of Economic Entomology. 105:1971-1978. Interpretive Summary: Light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) is native to Australia and has been introduced into New Zealand, New Caledonia, Hawaii, the United Kingdom and Ireland. E. postvittana is highly polyphagous and a serious economic pest to a wide range of horticultural crops. In March 2007, E. postvittana was detected for the first time in several counties in California, triggering the issuance of a federal domestic quarantine order. The primary concern with light brown apple moth establishment and spread in California is the trade restrictions imposed by foreign countries. In addition to the interstate quarantine for Hawaii, E. postvittana is currently a regulated pest in seven foreign countries, including Canada, Chile, Korea, Mexico, Peru, Thailand, and South Africa. These countries also require phytosanitary certificates stating that products have been inspected and found free of any stage of E. postvittana. Mexico and Canada have imposed restrictions on the importation of crops and plants from infested areas (Varela et al 2008). Irradiation is a postharvest quarantine treatment option for exported commodities to prevent movement of viable Epiphyas postvittana. A radiation dose of 150 Gy applied to fifth instars (the most tolerant life stage) prevented maturation to the adult stage in 34,997 treated individuals. A radiation dose of 150 Gy is recommended to control any E. postvittana eggs and larvae present of regulated fruits and vegetables.
Technical Abstract: The effects of irradiation on egg, larval, and pupal development, and adult reproduction in light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), were examined. Eggs, neonates, early instars, late instars, early pupae and late pupae were irradiated at target doses of 60, 90, 120, or 150 Gy or left untreated as controls in replicated factorial experiments and survival to the adult stage was recorded. Tolerance to radiation generally increased with increasing age and developmental stage. A radiation dose of 120 Gy applied to eggs and neonates prevented adult emergence. A dose of 150 Gy prevented adult emergence in larvae at all stages. In large-scale validation tests, a radiation dose of 150 Gy applied to fifth instars in diet or apples resulted in no survival to the adult stage in 34,997 treated individuals. Pupae were more radio-tolerant than larvae, and late stage pupae were more tolerant than early stage pupae. Radiation treatment of late pupae at 350 and 400 Gy resulted in 3 and 1 fertile eggs in 4,962 and 4,205 total eggs laid by 148 and 289 mating pairs, respectively. For most commodities, the fifth instar is the most radio-tolerant life stage likely to occur with the commodity; a minimum radiation dose of 150 Gy will prevent adult emergence from this stage and meets the zero tolerance requirement for market access. For traded commodities such as table grapes that may contain E. postvittana pupae, a radiation dose >400 Gy may be necessary to completely sterilize emerging adults, confirming that Epiphyas postvittana may be one of the most radio-tolerant insects infesting fresh commodities. A generic radiation treatment of 250 Gy is proposed for tortricid eggs and larvae in regulated commodities.