Tomonori Arai’s research while affiliated with National Agriculture and Food Research Organization and other places

Animal-mediated pollination is an essential ecosystem service for the production of many fruit trees. To reveal the community composition of flower-visiting wild insects which potentially contribute to fruit production and to examine the effects of geographic location, local meteorological conditions and locally introduced domesticated pollinators on them, we investigated the community composition of insects visiting the flowers (hereafter, “visitors”) of apple, Japanese pear and Oriental persimmon for 1‒3 years at 20 sites around Japan. While most of the variation (82%) of the community composition was explained by tree species with a slight contribution by geographic distance (2%), maximum temperature and tree species contributed 62% and 41% of the variation in total abundance of the visitors, respectively. Though the dominant families of the visitors varied spatiotemporally, the community composition of the visitors of apple and Japanese pear clearly differed from that of Oriental persimmon. While Andrenidae and Syrphidae together accounted for 46%‒64% of the visitors of apple and Japanese pear, Apidae represented 57% of the visitors of Oriental persimmon. The taxonomic richness, diversity and evenness of the visitors were best predicted by locally introduced domesticated pollinators and local meteorological conditions of wind speed and maximum temperature. Amongst these selected factors, locally introduced domesticated pollinators could have the largest impact. It seemed to be strongly related to the reduction of taxonomic richness, diversity and evenness of the visitors, accounting for 41‒89% of the variation. Results suggested that the community composition and total abundance of potential pollinators were predominantly determined by tree species and temperature, but locally introduced domesticated pollinators could have a determinantal pressure on the taxonomic diversity of the community.

Flowers on the ground of orchards can provide substantial resources for wild pollinators of orchard trees. Few studies, however, have examined the relative importance of groundcover flowers to orchard pollination by analyzing pollen on the body surface of pollinators. Oriental persimmon trees bloom within the longer blooming period of white clover, which is occasionally found as a flowering plant on the ground of persimmon orchards in Japan. The present study compared the insect species assemblage collected on persimmon flowers with that on clover. Before persimmon bloomed, Bombus ardens ardens and Apis cerana japonica were the major visitors of clover flowers. Once persimmon bloomed, the former was the most abundant bee that visited persimmon flowers over the flowering period. Apis mellifera was captured only on clover flowers. We found numerous clover pollen grains on the body surface of bumblebees captured on persimmon flowers, but far fewer persimmon pollen grains on bees that visited clover. These findings show that B. ardens ardens utilized the clover flowers under the orchards before persimmon bloomed. Before persimmon bloomed, Bombus ardens ardens and Apis cerana japonica were the major visitors of clover flowers. Once persimmon bloomed, the former was the most abundant bee that visited persimmon flowers over the flowering period. It was suggested that this bumblebee utilized the clover flowers under the orchards before persimmon bloomed.

Oriental persimmon, Diospyros kaki Thunb. (Ericales: Ebenaceae), is a generally diclinous tree. Because the representative cultivar, ‘Fuyu’, sets nearly exclusively female flowers and has low parthenocarpic ability, it requires pollen from other cultivars for pollination. Here, we identified the most important pollinator of D. kaki in hilly orchards surrounded by secondary forest in Hiroshima, southwestern Japan. To estimate the contribution of each flower visitor to pollination, we used an index of potential pollen transport, namely the rate of visitation per female flower multiplied by the estimated number of pollen grains on the body surface. Among nine functional groups, the value of this index was greatest for bumblebees followed by small bees, whereas that for honeybees was low because of the relatively few Diospyros pollen grains on the body surface. Bombus ardens ardens Smith (Hymenoptera: Apidae) was the predominant bumblebee species in terms of both monitored frequency of visits by insects and number collected for identification. We also counted the fruit set and seed number of ‘Fuyu’ fruit in various pollination treatments using exclusion mesh to assess the effectiveness of insects of different sizes. Bombus ardens ardens was the most important pollinator and small bees were the second most important.

We investigated the relationships between the timing of initial bud and fruit infestation by second-generation larvae of the persimmon fruit moth, Stathmopoda masinissa Meyrick, and the first catch dates of first-generation adult males in pheromone traps in persimmon orchards in Gifu, Hiroshima, and Shimane Prefectures, Japan, between 2010 and 2013. Seven to twelve days after the first trap catch of first-generation adults coincided with the period between initial bud infestation and initial fruit infestation, and insecticide spraying at this time was effective in suppressing fruit damage caused by second-generation larvae. Therefore, to control this pest, we recommended insecticide spraying from seven to twelve days after the first trap catch of the first generation.

The relationships between the timing of initial bud and fruit infestation by first-instar larvae of the persimmon fruit moth, Stathmopoda masinissa Meyrick, the day of full bloom of the cultivar 'Fuyu' and first catch dates of overwintering-generation adult males in pheromone traps were investigated in persimmon orchards in Gifu, Hiroshima, and Shimane Prefectures, Japan, between 2010 and 2013. Ten days after the day of full bloom of 'Fuyu' coincided with the period between initial bud infestation and initial fruit infestation of S. masinissa, and insecticide spraying at this time was effective in suppressing fruit damage caused by this pest. Twenty days after the first trap catch of the overwintering-generation of S. masinissa coincided with the period between initial bud infestation and initial fruit infestation. Thus, to control this pest, we recommended insecticide spraying at 10 days after full bloom of 'Fuyu' or at 20 days after the first trap catch of the overwintering-generation of S. masinissa.

Apparatus for extracting Scirtothrips dorsalis washed from plants consists of a 1-mm-aperture polyester mesh sieve stacked on top of a 75-μm-aperture nylon mesh sieve. Both sieves have an inner diameter of 75 mm and are 40 mm in height. A plant sample is placed in a 2- to 5-L beaker and 0.09% detergent solution is added. Following vigorous agitation, the solution is poured on the upper sieve. The washing and extraction procedures are performed again using tap water. Absolute ethanol is sprayed over the mesh of the top sieve to eliminate foaming of the detergent. The bottom sieve, which retains small insects and debris, is mounted on a Petri dish covered with a circular OHP film. The film has a 10-mm square grid printed on it and is backed with adhesive white tape. S. dorsalis and other thrips on the mesh are observed and counted under a binocular microscope