Systemic insecticides and application methods were examined for the control of the vector psyllid of citrus greening disease, Diaphorina citri, on grown king mandarin trees in an orchard in southern Vietnam from May 2007 to September 2008. Leaf spraying of imidacloprid, thiamethoxam, and clothianidin attained about 50 % to 70 % mortality of the psyllid for one month after the application and showed decreased efficacy thereafter. Imidacloprid was more effective than the other two insecticides, but the efficacy on grown trees was still much lower than that following application to young seedlings. Trunk injection of these insecticides accomplished similar mortality, about 50 %, and the efficacy of the insecticides continued for one month. An adjuvant was used with the goal of protecting the insecticide applied on leaves from precipitation, and mineral oil was used for the same reason, as well as its potential to control the psyllid. Neither the adjuvant nor the mineral oil played an evident role in the increase of insecticide efficacy or longevity. Application of systemic insecticides at even 50 times the dose described above did not show an apparent increase in psyllid mortality. The insecticides commonly used for the control of the psyllid were not as effective on this insect on grown trees as we had expected they would be.
Genetic variation of the white-spotted longicorn beetle Anoplophora spp., distributed on the Japanese mainland and the Ryukyu Islands, was examined using nucleotide sequences of mitochondrial DNA. Two fragments, a 1.2-kblong fragment containing portions of the cytochrome oxidase subunit I and II genes and a 1.4-kb-long fragment containing portions of 16S and 12S rDNAs, were sequenced. In phylogenetic analyses based on the sequences, 294 individuals collected at 75 localities were divided into two major groups (groups A and B) and then split into seven subgroups (A1-A4 and B1-B3). In group A, the closely related subgroups A1, A2, and A3 were mainly distributed on the Japanese mainland and were roughly separated among geographic areas, although the range of A3 spread significantly from Kyushu to the Central Ryukyu Islands. The sequence of A4, detected from one individual collected in eastern Honshu, was almost the same as that reported for A. chinensis (Forster) on the Chinese continent. In group B, subgroups B1 and B2 were restricted to the Central and Southern Ryukyu Islands, respectively, while B3 was distributed widely in both regions. Based on the results, we discuss the geographic origin of the haplotypes and movement of the insects between geographic areas.
Abstract: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.
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