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Miyagi A.,Okinawa Prefectural Agricultural Research Center | Ooishi T.,Okinawa Prefectural Agricultural Research Center | Ohno S.,Okinawa Prefectural Agricultural Research Center | Yoza K.,Okinawa Prefectural Agricultural Research Center | And 6 more authors.
Japanese Journal of Applied Entomology and Zoology | Year: 2011

Although Tetranychus urticae Koch (green form) has rarely been found on the southwestern region of Okinawa (the Sakishima Islands), we found an unexpected simultaneous occurrence of this species in 2009 in wax gourd greenhouses on one of the islands (Miyako Island). In that year, T. urticae occurred in 43% of wax gourd fields among the surveyed fields. In 2010, however, the frequency of occurrence naturally decreased; the species was found in only 3% of the fields from January to May and later become not found. These results have important implications for controlling spider mites on vegetable greenhouses in that area. Specifically, T. urticae can temporarily increase, but it cannot colonize the Sakishima Islands permanently due to some unknown biotic or abiotic factor(s). Neither the infestation frequency nor the species composition of other Tetanychus spider mites in the wax gourd greenhouses varied significantly between 2009 and 2010, suggesting that the occurrence of T. urticae did not affect the occurrence of other congeners. Source


China M.,Forestry and Fisheries Promotion Center | Nakamura H.,Okinawa Prefectural Sea Farming Center | Hamakawa K.,Okinawa Prefectural Fisheries Research and Extension Center | Tamaki E.,Okinawa Prefectural Sea Farming Center | And 4 more authors.
Fish Pathology | Year: 2013

In 2008, the myxosporean emaciation disease was found in cultured Malabar grouper Epinephelus malabaricus in a fish farm in Okinawa Prefecture, Japan. The disease occurred in winter when water temperature ranged from 21 to 26°C, and the cumulative mortality reached 20-50% among culture tanks. In affected fish, cranial bones were externally apparent due to severe emaciation. The intestinal wall was very thin and the liver exhibited conspicuous green color. Morphological and molecular analyses demonstrated that the causative myxosporean was Enteromyxum leei. Histopathological examinations revealed that the epithelia of the intestine and bile duct of diseased fish were heavily infected with E. leei. The common bile duct was often obstructed by severe inflammation with degenerated tissues and bacteria, suggesting that the abnormal color of the liver was caused by cholestasis. Some diseased fish recovered in a laboratory when water temperature increased naturally to 27-30°C in summer months, and the parasite was not detected in those fish. Experimental transmission of E. leei to naive Malabar grouper was successfully achieved by cohabitation with infected grouper or by feeding with the feces of infected fish. This is a new host and locality record for E. leei. Source


Matsumoto K.,Saga University | Yasaka R.,Saga University | Yasaka R.,Kagoshima University | Setoyama T.,Yakult Honsha Co. | And 3 more authors.
Journal of General Plant Pathology | Year: 2016

Pepper veinal mottle virus (PVMV) has been detected in chilli pepper (Capsicum annuum) for the first time on Ishigaki Island of Okinawa Prefecture, Japan. In the early 2010s, leaves of chilli plants (cv. Kahat-ace) developed virus-like symptoms such as rugosity, mosaic, vein banding, mottling, distortion with puckering and malformation. The biologically cloned isolate OKP2 was able to infect solanaceous plants such as bell pepper, chilli pepper, petunia, tomato, Nicotiana benthamiana and N. clevelandii. The coat-protein-encoding region shared 99 % nucleotide identity with that of PVMV-ns1 isolate collected in Taiwan. The implications of this record are discussed. © 2015, The Phytopathological Society of Japan and Springer Japan. Source


Ukuda-Hosokawa R.,Okinawa Prefectural Plant Protection Center | Ukuda-Hosokawa R.,Okinawa Prefectural Agricultural Research Center | Sadoyama Y.,Okinawa Prefectural Plant Protection Center | Kishaba M.,Forestry and Fisheries Promotion Center | And 5 more authors.
Applied and Environmental Microbiology | Year: 2015

Huanglongbing, or citrus greening, is a devastating disease of citrus plants recently spreading worldwide, which is caused by an uncultivable bacterial pathogen, "Candidatus Liberibacter asiaticus," and vectored by a phloem-sucking insect, Diaphorina citri. We investigated the infection density dynamics of "Ca. Liberibacter asiaticus" in field populations of D. citri with experiments using field-collected insects to address how "Ca. Liberibacter asiaticus" infection density in the vector insect is relevant to pathogen transmission to citrus plants. Of 500 insects continuously collected from "Ca. Liberibacter asiaticus"-infected citrus trees with pathological symptoms in the spring and autumn of 2009, 497 (99.4%) were "Ca. Liberibacter asiaticus" positive. The infections were systemic across head-thorax and abdomen, ranging from 103 to 107 bacteria per insect. In spring, the infection densities were low in March, at~103 bacteria per insect, increasing up to 106 to 107 bacteria per insect in April and May, and decreasing to 105 to 106 bacteria per insect in late May, whereas the infection densities were constantly ~106 to 107 bacteria per insect in autumn. Statistical analysis suggested that several factors, such as insect sex, host trees, and collection dates, may be correlated with "Ca. Liberibacter asiaticus" infection densities in field D. citri populations. Inoculation experiments with citrus seedlings using field-collected "Ca. Liberibacter asiaticus"-infected insects suggested that (i) "Ca. Liberibacter asiaticus"-transmitting insects tend to exhibit higher infection densities than do nontransmitting insects, (ii) a threshold level (~106 bacteria per insect) of "Ca. Liberibacter asiaticus" density in D. citri is required for successful transmission to citrus plants, and (iii) D. citri attaining the threshold infection level transmits "Ca. Liberibacter asiaticus" to citrus plants in a stochastic manner. These findings provide valuable insights into understanding, predicting, and controlling this notorious citrus pathogen. © 2015, American Society for Microbiology. Source


Wakamura S.,Okinawa Prefectural Plant Protection Center | Wakamura S.,Kyoto Gakuen University | Yasui H.,Japan National Institute of Agrobiological Science | Shimatani M.,Okinawa Prefectural Plant Protection Center | And 7 more authors.
Applied Entomology and Zoology | Year: 2011

In 2010, abrupt outbreaks of the African armyworm, Spodoptera exempta (Walker), occured on the Tarama, Iriomote and Kikai Islands in southwestern Japan. Analysis by gas chromatography-electroantennographic detection (GC-EAD) revealed two EAG-active compounds on male antenna in crude extract of virgin females. These compounds were identified as (9Z)-9-tetradecenyl acetate (Z9-14:Ac) and (9Z,12E)-9,12-tetradecadienyl acetate (Z9E12-14:Ac) in ca. 90:10 ratio by subsequent GC-MS analyses. (11Z)-11-Hexadecenyl acetate (Z11-16:Ac), which had previously been identified as a third component in the Kenyan population, was not detected. Binary blends of Z9-14:Ac and Z9E12-14:Ac at ratios between 99:1 and 90:10 showed a potent attractiveness in the field, superior to that of virgin females and comparable to that of the three-component formulation determined in Kenya. For the population survey, a 98:2 blend was used. In Tarama, only a few moths of S. exempta were captured with a light trap during the night when more than 600 males were captured with synthetic sex pheromone; more S. exempta captures with a light trap had been reported than with sex-pheromone traps in Kenya. This indicates that the Okinawan population has different properties from the Kenyan population in pheromone composition and behavioral response to light. © 2011 The Japanese Society of Applied Entomology and Zoology. Source

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