In the seminar, I will introduce my studies during the doctoral course: field experiments and model simulations to examine the feasibility of H.cunea control with synthetic sex pheromone traps. I applied mass-trapping method using sex pheromone traps for H. cunea populations in the actual street trees. Sex pheromones consist of chemicals that virtually have no toxicity and act mostly for the target insect with a minute amount. It is said that the pest control programs using sex pheromone bring about little damage to the natural environment. I carried out the mass-trapping experiments using synthetic sex pheromone at street trees in Tokyo, through 1994 to 1996. As a result, I could not significantly reduce the damage to street trees (as reduction of larval webs) in every treated area and generation compared with those in the non-treated areas. In addition, I could not find a sign of decline in the fall webworm population from year to year. To investigate the failure of the field trials and to inquire better strategies for H. cunea control, I constructed three models, spatially-structured individual-based model (Model I), a lattice model (Model II) and a temporally-structured population dynamics model (Model III). The Model I was constructed to analyze the effect of individual flight patterns on the management program of H. cunea. It incorporated complicated behavioral characters of individual males in flight. The lattice model (Model II) was constructed with simpler assumptions compared to the IBM, but it allowed us to manage larger number of individuals and to execute larger-scale simulations than the Model I. The temporally -structured model (Model III) had a daily-based age-structure of each cohort and contained detail processes of the insect population, and we could analyze synthetic effects of different pest management methods on the complicated pest population dynamics. I summarize the results and implications derived from the whole

(1) It was suggested that the pheromone traps could not always reduce mating success, while traps caught plenty of males (field trials at street trees).
(2) The possibility of male clustering around the trap was suggested. This phenomenon is likely to be caused by the process of male moths’ pheromone-mediated flight, and would produce male attraction effect (Model I, II).
(3) Disposition of traps was an essential factor affecting the mating success. The surrounding formation of traps with well- chosen spacing is the most effective. (Model II)
(4) A daily-based and age-structured model well described the timing and the dynamical characteristics of seasonal prevalence in the Tokyo population. The best strategy for controlling H. cunea was examined using this model, and intensive pruning in the 1st generation together with treatments of pheromone traps was shown to have an potential to eradicate the H. cunea population. (Model III)

Though many of the conclusions obtained from my studies should be evaluated by tests in the field in future, the IBM and the lattice model are very useful for elucidating the negative aspect of the pheromone traps, “male attraction effect”, systematically. The effects of pest controls on populati on dynamics were also exhibited by using the detailed age-structured model. I believe these approaches are novel and powerful for practical pest controls.