The influence of unusual hot weather on the occurrence of several arthropod crop pests

In order to project the influence of global climatic changes on insects, we examined the effects of a rise in temperature of 2–3°C on the phenology and occurrence of arthropod crop pests using data obtained from Kagoshima Prefecture, southwestern Japan, in 1998. The average temperature of this year was 2°C higher than that between 1960–1998. Several arthropod species emerged earlier than previous years because of the unusually high average temperature. These species were Homona magnanima, Adoxophyes honmai, Scirtothrips dorsalis, Pseudaulacaspis pentagona, aphids (mainly Myzus persicae and Lipaphis erysimi), and Tetranychus kanzawai. All species showed developmental zeros of less than 10°C. In contrast, Spodoptera litura and Helicoverpa armigera, whose developmental zeros were above the mean winter temperature, emerged as usual in the spring. A possible increase in the number of generations per year was not clearly shown by the trap capture records, but all species are likely to have 1–2 more generations. The total number of male S. litura captured by pheromone traps in 1998 was the largest during the past 14 years. There was a positive correlation between the abundance of males and the mean annual temperatures. In contrast, H. magnanima, A. honmai and aphids were less abundant in 1998, and this occurs once per 4–10 years. No detectable difference in abundance was observed in H. armigera. We concluded that an elevation in mean temperature of 2°C would impact the phenology of insects, but the pattern of response would greatly vary among species.