감귤원에서 귤굴나방의 개체군동태에 관한 연구 : 친환경 방제 및 개체군 모형

Abstract

1. Natural parasitism of P hyllocnistis citrella (Lepidoptera: Gracillaridae) in Jeju citrus orchards in Korea This study was conducted to investigate the species of native parasitoids attacking Phyllocnistis citrella and their parasitism in citrus orchards in Jeju. During the survey period from 2013 to 2014, seven parasitoids belongs to Chalcidoidea were found: majority parasitoids were Sympiesis striatipes with 73% and Quadrastichus sp. with 22% in Eulophidae. The remaining species were Neochrysocharis sp., Pnigalio sp., Holcopelte sp., Ageniaspis sp. (Encryrtidae) and Trichomalopsis sp. (Pteromalidae). Average parasitism rate reached 10.7% in orchards with spraying insecticide, and 32.2% in environmental-friendly managed orchards. 2. The distribution pattern of eggs on the leaves of shoots and the survival rate of larvae of P hyllocnistis citrella (Lepidoptera: Gracillaridae) in a citrus orchard of Jeju The citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillaridae), is an important pest that decreases the productivity of citrus trees by attacking citrus leaves, and especially it causes a severe damage during the young growth stage. In this study, we investigated the distribution of eggs on the leaves of shoots according to the leaf position, and the survival rate of this pest in the field conditions. The occurrence patterns of P. citrella eggs in citrus orchards were largely affected by the occurrence of shoots. Even if the adults were still being attracted in the pheromone traps, the eggs were not observed on leaves when the growth of shoots was stopped. The density of P. citrella eggs in the citrus shoots peaked at the fifth or sixth leaf from the terminal leaf, and over 90% of the eggs were found in the first to eighth leaves as a whole. In 2015 and 2016, the average survival rate of larvae was 1.4%, and the rate of survival to adults was 0.2%, indicating that most of larvae were died. Furthermore, we discussed the management strategy of P. citrella considering the distribution of eggs and the larval survival rate in the citrus shoots. 3. The Effect of Phyto-chemicals Based on Azadirachta indica and Sophora angustifolia on the Citrus Leaf Miner and Its Parasitic Wasps Phyllocnistis citrella Stainton (Lepidoptera: Phyllocnisitidae) damages on citrus leaves by making tunnels in the tissue, occurs in summer and autumn flushes of citrus trees mainly after late July. The damaged scars provide a route for the infestation of citrus canker that results in large occurrence of this disease and economic losses. This study was carried out to develop a control method for P. citrella that can be appled in environment-friendly citrus orchards. We tested formulated phyto-chemicals of Gosam (Sophora angustifolia) and neem trees (Azadirachta indica) and petroleum oil (150x); two phyto-chemicals were mixed with petroleum oil of 1,000x for field application. All treatments were sprayed three times at 7 d interval, and the damage of P. citrella and parasitism were evaluated in randomly selected 5 flushes per citrus tree. There was no control effect when petroleum oil was sprayed alone. The control effects were high in plots of Gosam or neem-based phyto-chemicals mixed with petroleum oil. In addition, it was found that the parasitic wasps of P. citrella were frequently occurred in plots of the untreated control and petroleum oil, and they suppressed the population of P. citrella over the time. 4. A population model for the citrus leafminer, P hyllocnistis citrella Stainton (Lepidoptera: Phyllocnistidae) and its field validation in Jeju citrus orchards, Korea This study was carried out to develop temperature-driven immature development and oviposition models of citrus leafminer, Phyllocnistis citrella. Previously published data sets were used to estimate each model. The lower developmental threshold temperatures for eggs, larvae, and pupae were calculated using linear model to be 8.8, 7.1, and 12.4℃, respectively. Thermal constants for eggs, larvae, and pupae were 52.2, 108.2, and 88.9 degree-days, respectively. Non-linear model (Logan model modified with three parameters) fitted well for the relationship between development rate and temperature for eggs, larvae and pupae. Aging rate (1/female adult longevity) model was estimated and used to calculate the physiological age of female P. citrella adults. Temperature-dependent components (total fecundity, age-specific cumulative oviposition rate, and age-specific survival rate) were then developed for the oviposition models of P. citrella. Based on the estimated total fecundity model, the highest total number of eggs laid by a female was approximately 59.5 at temperature of approximately 28.6℃. Sixty percent of total eggs were laid at approximately physiological age of 0.82 in the oviposition rate model. Fifty percent mortality occurred at ≈0.91 physiological age in the survival rate model. Finally, we provided oviposition density curves by incorporating all oviposition component models. Also, thermal fitness curve expressed by the intrinsic rate of increase (rm) versus temperature predicted a maximum r_m of 0.2792 at 31.7℃. Consequently, these temperature-driven models estimated in this study can be used to predict phenological events and/or to construct population model for P. citrella in the future. 5. A population model for the citrus leafminer, P hyllocnistis citrella Stainton (Lepidoptera: Phyllocnistidae) and its field validation in Jeju citrus orchards, Korea A population model for the citrus leafminor, Phyllocnistis citrella, was developed to understand the population dynamics of this moth pest and to find an effective management strategy in citrus orchards. Temperature-dependent biological parameters for basic process models were obtained from previous reports. The model was structured by the five developmental stages of P. citrella: egg, small-larva, large-larva, pupa, and adult. The model started from overwintered adults or pupae population, and consisted of a series of component models: (1) stage emergence models of eggs, larvae, and pupae, (2) adult oviposition model, (3) the shoot growth model of host plant, and (4) adult activity models in relation to temperature and wind speed. Simulations results of the model described well the typical patterns of P. citrella adult abundance in citrus orchards, showing no different adult flight peak within 0 d in 36 of 45 cases between model and actual peaks. The availability of citrus shoots (flushes) was acted as a major limitation factor of population abundance. Also, wind speeds affected highly the adult activity of P. citrella population. Overwintering pupal populations importantly contributed to the abundance of P. citrella in the seasons, while overwintering adults did not contribute population build up in Jeju areas. Based on the population model developed in the present study, we projected population phenology of P. citrella at elevated air temperatures, and discussed the management strategy in the future.