Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2003
Publication Date: 10/1/2003
Citation: Hallman, G.J. Ionizing irradiation quarantine treatment against plum curculio (coleoptera: curculionidae). Journal of Economic Entomology. 96:1399-1404. Interpretive Summary: Plum curculios only exist in North America. As a pest of many of the temperate fruits produced in the U.S. (apples, pears, peaches, plums, blueberries, cherries), plum curculios cause phytosanitary restrictions to be put on fruit exports. The current treatment uses methyl bromide fumigation, which is becoming more costly and may not last forever. A lengthy cold treatment can be used on apples, but not the other fruits. Alternative treatments are needed. In this research, ionizing irradiation at 92 Gy prevented reproduction when applied to 25,000 plum curculio adults, the most radiotolerant stage of the insect. All hosts of the plum curculio tolerate much more than 92 Gy, making irradiation a viable treatment for any fruits infested by the quarantine pest.
Technical Abstract: Plum curculio, Conotrachelus nenuphar (Herbst), is a quarantine pest of many temperate fruits, such as pomes Malus spp., stone fruits Prunus spp., and blueberries Vaccinium spp., in North America east of the Rocky Mountains and a small area in Utah. There are 2 strains, a northern, univoltine that undergoes obligate diapause as an adult and a southern multivoltine that usually has facultative diapause. Current quarantine treatments include methyl bromide fumigation and cold storage for several weeks. The cold storage treatment may not be effective against northern strain adults in diapause. The objective of this research was to develop an irradiation quarantine treatment against plum curculio. The estimated dose to kill southern strain plum curculio adults in one day is approximately 4 kGy. Diapausing northern strain plum curculio were prevented from reproducing with 40 Gy. Reproduction of southern strain plum curculio was prevented with a target dose of 80 Gy, and the dose recommended as a quarantine treatment that would prevent adults from reproducing, is 92 Gy, the maximum absorbed dose measured when a target dose of 80 Gy was sought. At that dose, oviposition may still occur for up to a week and some of the eggs may hatch, but there is no development beyond the first instar. Hosts of the plum curculio would tolerate that dose well. Immature plum curculio were prevented from reproducing with lower doses.