茨城県のキョウナ（Brassica rapa L. Japonica group，別名ミズナ）栽培では，夏期を中心に多発生する立枯れ症が問題となっている。主原因の一つである萎凋病を引き起こすFusarium属菌について，各種アブラナ科作物に対する病原性により菌種の検討を行い，現地での発生状況について調査した。2009年に結城市のキョウナ圃場で分離し，茨城県農業総合センター園芸研究所に保存されていた09060-2菌株は，キョウナやカブ等に対して強い病原性を示したものの，キャベツおよびダイコンに対する病原性は弱く，F. commune f. sp. rapaeと考えられた。2016年に行方市の農家4戸で夏期を中心に発生したキョウナ萎凋病罹病株から分離したFusarium属菌10菌株のうち，3菌株はキャベツに対し強い病原性を示した一方，ダイコンに対する病原性は弱かったことからF. oxysporum f. sp. conglutinansであり，7菌株はキャベツ，ダイコンに対して病原性がない，もしくは弱かったことからF. commune f. sp. rapaeと考えられた。本県では2種類のFusarium属菌がキョウナ立枯れ症の発生に関与していることが明らかとなったが，同一ほ場における2菌種の混発事例は確認されなかった。
Powdery mildew of campfire crassula (Crassula capitella subsp. thyrsifolia) occurred in Ibaraki prefecture in March 2014. We analyzed pathogenic-ity, morphological characteristics and rDNA-ITS region of the causal agent of the disease, and iden-tified the causal agent as Pseudoidium sp. We for-mally named the disease 'powdery mildew of camp-fire crassula' as a new disease of the plant in Japan.
The infection of potted hydrangea by Acidovorax valerianellae during field cultivation was investigated. Consequently, the disease developed in potted hydrangea cultivated in the field, but not those in a greenhouse. Moreover, A. valerianellae was isolated from inside the flower bud just after cultivation in the field. The results suggest that A. valerianellae infected potted hydrangea during cultivation in the field.
Seventy-eight plant samples of Chinese peony (Paeonia lactiflora Pall.) in Japan were collected from five prefectures to survey viral pathogens. By next-generation sequencing, cycas necrotic stunt virus (CNSV) and tobacco rattle virus (TRV) were detected. As a result of performing RT-PCR for each individual sample, CNSV was detected from a plant exhibiting mottle, whereas TRV was detected from three plants exhibiting ringspots, line patterns or yellow blotching on their leaves. This is the first report of detection of CNSV by RT-PCR from Chinese peony in Japan.
Mitochondrial DNA sequences coding cytochrome c oxidase subunit I (COI) gene of 14 hymenopterous parasitoid wasps on the garden pea leafminer fly, Chromatomyia horticola were investigated. Dacnusa nipponica, Opius sp., Halticoptera circulus, Sphegigaster hamugurivora, Chrysocharis pentheus, Chrysocharis pubicornis, Closterocerus trifasciatus, Diglyphus albiscapus, Diglyphus isaea, Neochrysocharis formosa, Pediobius metallicus and Pnigalio katonis have different DNA sequences and can be discriminated among each other. Diglyphus minoeus and Merismus sp. were failed to determine the sequences.
In Japan, the sugar beet cyst nematode, Heterodera schachtii Schmidt, was confirmed first in September 2017, on the roots of Brassica sp. cultivated in Nagano Prefecture. In response to this, as an emergency measure to eradicate H. schachtii and to prevent further infestation, multiple rounds of fumigant application were carried out. Cultivation of host crops was then resumed on fields where densities of H. schachtii cysts were observed to have lowered below detectable levels. However, H. schachtii cysts were re-detected in 14% of fields in which cultivation of host crops was resumed. This study was carried out to verify the effect of fosthiazate granules on recurrence prevention in fields in which farming was resumed and to determine appropriate treatment time. For this, nematicide was applied at different times to the low-density field of H. schachtii cysts, and its effect on the density was examined. We found a high control effect especially when the nematicide was applied to soil 7 days before transplanting the host plants.
To improve the coverage area ratio (agrochemical adhesion area / total area) in orchards sprayed by unmanned aerial vehicles (UAVs), and to clarify the ratio at which the application of a small amount of concentrated chemicals achieves effective control of pests, it is necessary to establish the technology. Using two types of UAVs, we sprayed water over a citrus orchard at the rate of 100 L/ha, and assessed the coverage area ratio of water-sensitive test papers placed in the orchard canopy at three heights (200, 100, 50 cm) in vertical and horizontal orientations. The median of the ratio ranged from 0.35% to 23.0% by unmanned helicopter and from 0.05% to 25.9% by multi-rotor sprayer, while ranged from 21.6% to 99.9% by air blast sprayer spraying 3000 L/ha. The ratio depended on the orientation of the test papers and the installation height, because UAVs can spray only from above the trees. These results show that it is necessary next to clarify the optimal method for spraying citrus orchards by UAVs.