There are many related studies; however, almost all of them focus on higher taxonomic tendencies, ignoring a difference in the reaction for each species. In this study, we measured relative basal area (RBA) as the index for invasion of broad-leaved trees into eight Larch plantations, and investigated the relationship between RBA and composition and abundance of oribatid mites community. As a result, we found 49 families, 60genus, 89 species, 24,368 adult and larvae and nymphs, 56,364. The degree of invasion of broad-leaved trees did not affect significantly total abundance and number of species for oribatid mites observed. While, those measurements significantly correlated with the total amount of litter, including conifer and broad-leaves. We also found that there are many oribatid mite species showing habitat preference relating to a kind of litter.

Tetranychus evansi Baker & Pritchard occurs on solanaceous plants, and causes serious damage to various crops in Africa and Europe. Tetranychus takafujii Ehara & Ohashi was found on Solanum nigrum L. in Japan in 2001 and described as a new species in 2002. However, because T. takafujii is very similar to T. evansi in morphology, doubt has arisen about the difference between these two species, although there is no report discussing their taxonomic status. Tetranychus takafujii is specialized on solanaceous plants and it is possible that this species gets out of hand after invasion of solanaceous agricultural crops. To evaluate its potential severity as a pest, it is necessary to assess its performance on a variety of food plants in a carefully controlled laboratory set-up. The present study determined the development on 21 crops and weeds, and the reproduction on Solanum nigrum of a Japanese T. takafujii population and six T. evansi populations from abroad. Four plants (potato, horsenettle, pear and cucumber) served as host plant for all seven populations and most larvae successfully reached adulthood. Life-history parameters, such as the rate of development and the intrinsic rate of natural increase (rm), became higher with temperature increasing from 15 to 35°C. The rm-value at 25°C was similar among all populations tested and it was close to the value obtained in T. takafujii [Kotsubo et al. (2004) J. Acarol. Soc. Jpn. 13: 71-76]. This indicates that T. takafujii has the potential to become a serious pest on solanaceous crops, just the same as T. evansi in Africa and Europe.

Tetranychus evansi Baker & Pritchard occurs on solanaceous plants, and causes serious damage to a variety of crops in Africa and Europe; it has not been reported from Japan. Tetranychus takafujii Ehara & Ohashi was found on Solanum nigrum L. in Japan in 2001 and described as a new species in 2002. It is considered to be a Solanaceae-specialist too and it is feared to become a severe pest on solanaceous crops, once it invades them. Because T. takafujii is morphologically very similar to T. evansi, doubt has arisen about the difference between these two species. Here we avoid the issue of taxonomy and focus on a solution for the potential problems that may arise when either of the species invades solanaceous crops. The present study determines the susceptibility of three T. takafujii populations from Japan and six T. evansi populations from various countries to 11 acaricides. The LC50-values of all nine populations tested were lower than the recommended concentration of every acaricide. These results suggest that mites from all nine populations can be controlled with acaricides when they occur on crops.

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is one of the most important agricultural pests in Japan, that causes retard of plant growth and sooty moulds through excreted honeydew by direct sucking of pholoem sap, and additionally transmits several kinds of plant virus. B. tabaci consists of more than 20 biotypes which possess different ecological or physiological characters but cannot be distinguished from others morphologically. In Japan, exotic B and Q biotypes are the common pests of vegetables, flowers and ornamental plants. B biotype, the silver-leaf whitefly, was first recorded in Aichi Prefecture, Tokai region, in 1989 and expanded its distribution to almost all part of Japan, except for the northern area, within several years. Q biotype was recently found in Hiroshima Prefecture, Chugoku region, in 2004 and is still expanding the distribution in our country. Indigenous B. tabaci biotypes also exist in the southwestern part of Japan: JpL biotype was recorded in Honshu, Shikoku, Kyushu Islands and Nauru biotype was found in Amami and Ryukyu Islands. Although the host plants of these indigenous biotypes include some agricultural crops, these insects are not important as agricultural pests. The most serious problem in vegetable cultivation caused by B. tabaci is an intensive epidemic of the tomato yellow leaf curl disease (TYLCD) which leads to a large yield loss of tomato production in green houses. TYLCD distributes worldwide and it was found in Aich and Sizuoka Prefectures, Tokai region, and Nagasaki Prefecture, Kyushu region, simultaneously in 1996. The distribution of TYLCD expanded mainly in the western part of Japan for several years after its first finding, but recently TYLCD started to occur also in the eastern part of Japan, Kanto and Tohoku regions. Tomato yellow leaf curl virus (TYLCV), a pathogen of TYLCD, is transmitted by B or Q biotype of B. tabaci in a persistent manner. Although an effective control of B. tabaci is essential for decreasing of TYLCD outbreaks in tomato green houses, it is quite difficult to control these whiteflies only by the spraying of chemically synthesized insecticides due to their insecticide resistance. Especially, Q biotype shows a high level of resistance to pyriproxyfen and neonicotinoid insecticides. To avoid the development of insecticide resistance in B. tabaci, we are trying to combine some different control methods, for example, use of a fine mesh screen to prevent the invasion of vector insects, use of the physical-coating or microbial insecticides with the chemically synthesized insecticides to prevent the reproduction of vector insects, closing and steaming of a green house at the end of tomato cultivation to kill vector insects and prevent their escape from there, as an integrated pest management (IPM) system for B. tabaci and TYLCD control. We are also breeding TYLCV resistant varieties of tomato and considering how to use these varieties effectively.

The life cycle of ticks is characterized by alternate off-host and on-host conditions. The life span is estimated at several years and most ixodid ticks spend more than 95% of their life off the host. They seem to have a unique strategy to endure the off-host state for a long period. By electron microscopy, isolation membrane-, autophagosome- and autolysosome-like structures were found in the midgut epithelial cells of unfed ticks. Therefore, we focused on autophagy which is well-conserved from yeast to higher eukaryotes and induced by starvation. We have identified homologues of autophagy-related (ATG) genes (ATG3, ATG4 and ATG8) from cDNA libraries of the 3-host tick Haemaphysalis longicornis. Each expression profile of H. longicornis ATG (HlATG) genes and HlAtg proteins at the stages of nymph and adult were examined by real-time PCR and immunoblotting. Moreover, autophagy is known to be induced by inactivation of target of rapamycin (TOR), a phosphatidylinositol kinase. To examine the effect of TOR function on the expression of HlAtg protein(s), rapamycin, a specific inhibitor of the signal transduction mediated by TOR, was injected to unfed adults. It was revealed that the expression of HlAtg protein(s) was enhanced in response to the rapamycin. This result indicates that tick have the nutrient-sensitive TOR signaling pathway which regulate autophagy.