Abstract
Regular census of road-side trees on selected roads has been carried out to detect the abundance and the seasonal trend of larval development of Hyphantria cunea near Tokyo. The results obtained so far are as follows : The zero-truncated negative binomial was considered to be a good model to represent the distribution pattern of the number of H. cunea colonies per tree. The density of H. cunea reached the peak at the 2nd generation of 1965, continuously fell till the 1st generation of 1968, and then increased. Basically similar population trends were observed at three localities in Tokyo. Basic features of the mortality pattern of H. cunea, which were previously suggested from studies made in the survey stations, were also observed in the road survery. That is, the mortality pattern was characterized by relatively low mortality during the egg and early larval stages and remarkably high mortality during the later larval stages. Progress of the mean instar could be estimated by the cumulative heat units above 10°C. It was concluded that the insecticidal treatment must be made on the date just after the cumulative heat units have exceeded 600 day-degrees (°C) in the 1st generation and 1300 to 1400 day-degrees in the 2nd generation.
