감귤원에서 네눈쑥가지나방의 생태 연구: 섭식양상, 성페로몬 조성 및 개체군 모형

Abstract

This study was conducted to evaluate a Geometridae (Lepidoptera) species, Ascotis selenaria, as a pest in citrus orchards and to establish a monitoring and prediction method with their sex pheromone and population model in Jeju, Korea. Seven Geometridae species were occurred in citrus orchards: Ascotis selenaria, Ectropis excellens, Menophra senilis, Biston panterinaria, Ourapteryx nivea, Odontopera arida and Hypomecis punctinalis. Among them, A. selenaria was most abundant and caused citrus fruit damage. Fruit damage of Citrus unshiu appeared as gnawed scars caused by young larvae feeding on fruit surface. Fruit damage on Shiranuhi appeared as a wide hole or deep scars caused by mature larvae (6th instar). Citrus leaf damage due to Geometridae larvae was high during May to June. Fruit damage started in late June as the spring-shoots of citrus hardened and increased sharply in late July. In the field experiments, mean of fruit damage reached 4.5% in the late season from 2008 to 2010. A. selenaria larvae were distributed randomly in citrus orchards because clump index was almost 0 from 2008 to 2010. In citrus orchards, A. selenaria larvae started to appear in mid-May and their populations peaked in mid-June, late July, and early to mid-September. Adult males of A. selenaria had a maximum peak in mid-May, and two other peaks in early to late July and late August to early September. A. selenaria male adults were collected in a pheromone traps constantly throughout Jeju Island. In the sex pheromone glands of A. selenaria females, two components, (Z,Z)-6,9-cis-3,4-epoxynonadecadiene (6Z,9Z-cis-3,4-epoxy-19:H) and (Z,Z,Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H), were identified by GC-MS analysis. However, 3Z,6Z,9Z-19:H neither elicited an EAG-response on the male antenna in GC-EAD nor increased the attractiveness of the first component for A. selenaria males in the field. Two isomers 6Z,9Z-cis-3R,4S-epoxy-19:H and 6Z,9Z-cis-3S,4R-epoxy-19:H, of 6Z,9Z-cis-3,4-epoxy-19:H, showed same retention time in GC-MS analysis and were critical for attracting of A. selenaria males. The optimum blend ratio of tow isomers showing peak catches of A. selenaria males had large variations among locations investigated. A. selenaria populations in Gunwi showed a peak activity at 0.9 : 0.1 ratio, while the populations of Goheung, Yeongam, and Jeju (Aewol & Harye) showed peak activity around 0.5 : 0.5 ratio. These variation in an optimum blend of A. selenaria would be caused by geographical isolation. Egg, larva, and pupa developmental rate (1/median day) were incorporated into temperature-dependant developmental rate models, respectively, using Hilbert & Logan model. Weibull function was applied to describe their developmental distribution based on the summation of their daily developmental rate. An oviposition model consists of a total fecundity model, an age-specific cumulative oviposition model, and an age-specific survival model, in which physiological age was calculated from adult developmental rate model. A Gaussian model was applied to the total fecundity model and a sigmoid function was to an adult developmental rate model. A normalized cumulative oviposition rate and a survival rate with physiological age were incorporated into those age-specific models. A population model for A. selenaria was established by linking egg, larval, pupal, and oviposition models. Model outputs were compared with the actual 1st larva and adult occurrence surveyed in a citrus orchard in Seogwipo, Jeju from 2008 to 2010. A simulated output driven in the case that overwintered pupae were grouped with different developmental rates was successfully fit to actual 1st larva and adult occurrence and the peak time.