Junichiro Abe

Application of synthetic herbivore‐induced plant volatiles causes increased parasitism of herbivores in the field

We previously reported that Cotesia vestalis (Hymenoptera, Braconidae), a parasitoid of diamondback moth (DBM) (Plutella xylostella; Lepidoptera, Plutellidae) larvae, was attracted to volatiles from crucifer plants infested by moth larvae kept in a desktop acrylic box, and that a blend of four DBM‐induced plant volatiles was responsible for this attraction. In this study, using a specially designed dispenser to release the four compounds, we demonstrated that the wasp was attracted to intact komatsuna plants (Brassica rapa var. perviridis). The experiments were performed in a climate‐controlled room, which was approximately 1000 times larger than the acrylic box used previously. Similarly, using the dispenser in the field, C. vestalis females were attracted to intact komatsuna plants with the dispenser from a distance of three metres. We also examined the effect of the volatile blend on the incidence of parasitism of DBM larvae in the field. Three small containers containing DBM‐infested komatsuna plants with dispensers, and three control containers containing only infested plants (control) were arranged in two lines running perpendicular to a komatsuna field in which both DBM larvae and C. vestalis populations were maintained, at distances of 12, 30 and 70 m. The results showed that the incidence of DBM parasitism was significantly higher in containers containing dispensers than in the control containers, suggesting that the blend could potentially be applied to DBM control in agroecosystems.

Morphological features, distribution, prey mites, and life history traits of Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) in Japan

The distribution records of Feltiellaacarisuga (Vallot) (Diptera: Cecidomyiidae) in Japan were previously based only on the collecting data of Feltiella sp. from Kagoshima in 1971. We identified acarivorous gall midges collected from various localities in Japan as F.acarisuga and found that it is widely distributed in Japan from Hokkaido to Okinawa. A supplementary description to that made by Gagné in 1995 is provided, together with illustrations of the male fifth flagellomere, male genitalia, pupa, and pupal frons. We also provide information on mites on which it preys and ecological traits of F. acarisuga and devote a brief discussion to its use as a biological control agent. We newly confirm that F. acarisuga fed on Acaphylla theavagrans Kadono (Acarina: Eriophyoidea) in addition to tetranychid mites that were recorded earlier. For the convenience of applied entomologists, differences between larvae of F.acarisuga and those of other free-living cecidomyiids that may sometimes be present on the same leaf are briefly explained.

Occurrence of two acarivorous species of the genus Feltiella (Diptera: Cecidomyiidae) in Okinawa, southern Japan, and redescription of F. acarivora (Zehntner)

Based on morphological features and molecular information, we record the occurrence of two acarivorous species of the genus Feltiella (Diptera: Cecidomyiidae) on some islands of Okinawa Prefecture, southern Japan. They are Feltiella acarivora (Zehntner), which is new to Japan, and Feltiella acarisuga (Vallot). F. acarivora is redescribed because the original description was incomplete. Feltiella acarivora was distinguished from F. acarisuga by having the following characteristics of male terminalia: hypoproct a little shorter than aedeagus, slightly tapering to a blunt apex with an apical ligule and gonocoxite with a hairy mediobasal lobe. For each species, we provide information on its geographic distribution, possible prey mites, and plant species on which the mites and Feltiella larvae or pupae were found. Through our surveys, we observed F. acarivora coexisting with at least eight species of tetranychid mites on various plant species, including fruit trees and vegetable crops. These observations suggest that F. acarivora and F. acarisuga contribute to the control of pest tetranychid mites in Okinawa.

Analytical model to predict the number of parasitoids that should be released to control diamondback moth larvae in greenhouses

Abstract When using parasitoids in biological control programs, it is important to understand the number of parasitoids required for release to maintain pest population under economic injury levels. Here, we developed an analytical model to estimate the number, and apply the model to a system involving crucifer plants (Brassica rapa), diamondback moth [Plutella xylostella (L.) (Lepidoptera: Plutellidae)] (DBM) larvae, and the parasitoids Cotesia vestalis (Haliday) (Hymenoptera: Braconidae). To evaluate the calculated number of C. vestalis for release, we conducted the evaluation of our previously reported study by Abe et al.

The contribution of a beneficial insectary plant Scaevola aemula to survival and long-term establishment of flightless Harmonia axyridis in greenhouses

The fairy fan flower, Scaevola aemula R. Br., is a primary candidate insectary plant for maintaining populations of generalist predators. We conducted release experiments in greenhouses of cultivated eggplants to evaluate the effects of intercropping S. aemula on the establishment of flightless Harmonia axyridis Pallas. Compared with a monoculture of eggplant, all release experiments showed that flightless H. axyridis remained in greater numbers in plots with S. aemula planted alongside eggplant. In the release experiment of flightless H. axyridis larvae, the incidence of aphids in the plot with transplanted S. aemula was suppressed compared with that in the release plot without transplanted S. aemula. In a laboratory experiment, the longevity of flightless H. axyridis adults on blossom stems of S. aemula was greater than when open flowers and buds were removed, suggesting that the insects fed on floral resources such as the pollen of S. aemula. Our findings showed that the floral resources of S. aemula can enhance aphid suppression by improving the establishment of flightless H. axyridis.

Development and characterization of 21 polymorphic microsatellite loci in the aphidophagous gall midge, Aphidoletes aphidimyza (Diptera: Cecidomyiidae)

We have developed and characterized 21 microsatellite markers in the aphidophagous gall midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae). All 21 loci tested were polymorphic: the number of alleles ranged from 2 to 17. Allelic richness and observed heterozygosities were higher in females than in males. Several loci had no heterozygosity in males, suggesting that the loci were located on sex chromosomes or E-chromosomes, common to cecidomyiids. The high polymorphism detected in this study suggests the markers will be of value in analyzing genetic structure of field populations.

Descriptions of two new endoparasitic cecidomyiids (Diptera: Cecidomyiidae) from Japan.

Two endoparasitic species of Cecidomyiidae (Diptera) new to science are reported from Japan. Females of Endaphis psyllophaga sp. nov. lay their eggs on the wing of Calophya nigridorsalis (Hemiptera: Psylloidea: Calophyidae) on Rhus succedanea (Anacardiaceae), and newly hatched larvae bore into the adult body. The six nominal species of the genus Endaphis are endoparasitoids of aphids. The genus Endopsylla, which is morphologically similar to the genus Endaphis, consists of two species whose larvae attack psyllids or tingids. Females of Endaphis muraii sp. nov. lay their eggs near colonies of host aphids and newly hatched larvae bore into the body of aphids such as Macrosiphum euphorbiae and Aphis glycines (Hemiptera: Aphididae). The two new species are described, illustrated, and compared to known congeners, and information is given for the two species on their distribution, host range and ecological traits. Now, E. muraii is considered to be a potential biological control agent against aphids.

Occurrence of diamondback moths Plutella xylostella and their parasitoid wasps Cotesia vestalis in mizuna greenhouses and their surrounding areas

Pest insects invade commercial greenhouses from the surrounding areas. We aimed to clarify whether (1) the seasonal population dynamics of local pest insects affects their greenhouse invasions and (2) carnivorous natural enemies of the pests mirror this invasion. We compared the occurrence of diamondback moth [DBM: Plutella xylostella (Lepidoptera: Plutellidae)] larvae and their native parasitoid wasps Cotesia vestalis (Hymenoptera: Braconidae) on mizuna plants [Brassica rapa var. laciniifolia (Brassicales: Brassicaceae)] in commercial greenhouses, with their population dynamics on a wild cruciferous weed Rorippa indica (Brassicales: Brassicaceae) in satoyama in Kyoto, Japan. C. vestalis followed the occurrence of DBM larvae on both mizuna and R. indica; no C. vestalis were recorded in greenhouses free from DBM larvae. C. vestalis females were more attracted to volatiles emitted from DBM-infested than from uninfested mizuna. However, the presence of DBM in greenhouses could not always be explained by its seasonal population dynamics in the surroundings.