Extensive wilts of trees have recently occurred in the windbreaks at Okinawa Branch of the Tropical Agricultural Research Center in Ishigaki Island, Okinawa, Japan. Dead or declined trees were observed at 43 points, the total number of dead and declined trees was over 200 and total length of damaged windbreaks was 515m, in about 11% of the total length of windbreaks. Roots of dead and declined trees were collected and many fungus cultures were isolated from them. Most isolates had the following common cultural characteristics:no clamp connections on septa, staghorn-like hyphae and arthroconidia. Two cultures isolated from tissue of diseased trees were artificially inoculated into saplings of Podocarpus macrophyllus. Nine saplings were killed out of 19 inoculated saplings within 13 months and the fungus was reisolated from the dead saplings. As the isolates were considered to be a hymenomycetous fungus, fungal fruiting bodies were collected from windbreaks and from nearby and cultures were isolated from the collected fruiting bodies. One of cultures isolated from the collected fruiting bodies coincided in cultural characteristics with the isolates from dead and declined trees. The fruiting body from which this culture was isolated, was identified as Phellinus noxius (Corner) Cunningham.Taxonomic study revealed that Ph. sublamaenis (Lloyd) Ryvarden, published as a prior name for Ph. noxius, is a synonym of Ph. lamaensis. The fungus reported as Ph. lamaensis by Yasuda from Bonin Island of Japan in 1916, was identified as Ph. noxius.
The insecticide susceptibility of the small brown planthopper, Laodelphax striatellus Fallén, collected from East Asia in 1992-1994, was examined by the topical application method. The LD 50 values of organophosphorus insecticide for the northern Vietnam populations (HAI, HAN, VIN) and the JIN population (Yunnan Province, China) were smaller than those of the FU (Zhejiang Province, China), IB (central Japan) and KU (southwestern Japan) populations. The LD 50 values of organophosphorus and carbamate insecticides for the northern Vietnam populations were almost the same as that for the Fukuoka (western Japan) population examined in 1967. The LD 50 values of organophosphorus insecticides did not differ among the FU (Zhejiang Province, China), IB (central Japan), and KU (southwestern Japan) populations. The LD 50 values of carbamates for the KU population were the largest, and those for the northern Vietnam population were the smallest. The carbamate susceptibility of acetylcholinesterase in the KU population was lower than that in the HAI population. Therefore, we considered that insensitivity of acetylcholinesterase for carbamate was one of the carbamate resistant factors in the KU population. The LD 50 values of etofenprox, fenvalerate, and imidacloprid showed no differences among all the populations tested, respectively.
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