The cool summer of 1993 damaged the rice crop nation-wide. Furthermore rice blast was found to be widespread in Ibaraki, Tochigi and Saitama Prefectures. The race of rice blast fungus isolated in Ibaraki, Tochigi and Saitama Prefectures were 001, 003, 007, 033 and 037. In 1988 the major race was 003 in these prefectures, but by 1993 this had been replaced by 007. Because of the increase of race 007 the area planted with Kinuhikari and Asanohikari varieties of rice, which have a resistance gene Pi-i, was increased.
茨城県つくば市の農業研究センター圃場で栽培されていたツルマメに, 根の皮層部が褐変腐敗する根腐れ症状が発生した。病患部からはツルマメとダイズの双方に病原性を有する糸状菌が高率に分離され, 形態的および生理的研究の結果, Calonectria crotalariae (Loos) Bell et Sobers〔不完全世代: Cylindrocladium cyotalariae (Loos) Bell et Sobers〕と同定された。本菌によるツルマメの自然発病が観察されたのはこれが最初と考えられる。将来本菌によるツルマメの根腐れ症状に病名を付す場合には,「黒根腐病」とするように提案する。
Leaf disc tests taken over a period of 3 years on 324 isolates of cucumber powdery mildew fungus, Sphaerotheca fuliginea (Schlechtendahl: Fries) Pollacci, revealed that a resistant strain to DMIs was distributed widely in the Kanto-Tosan District. The degree of resistance to triflumizole was always less than to triadimefon and fenarimol, although cross resistance among the DMIs was clearly shown. In general field performance of triflumizole was considered to be still good, because triflumizole was the most frequently used fungicide among DMIs registered for cucumber. From 1991 to 1992, the unimodal sensitivity distribution for each DMI tested gradually shifted towards lower sensitivity. However from 1992 to 1993 the reverse was true: sensitivities to DMIs were observed to increase. This phenomenon corresponded to a decline in the number of DMI applications to cucumber in the district. These results indicate that restricted use of DMIs may prevent a further decline in sensitivity of S. fuliginea.
The performance of DMIs on cucumber powdery mildew, Sphaerotheca fuliginea, was found to be acceptable for a period of three years following the introduction of these fungicides. However, sencitivity level of the fungus gradually decreased during this period, especially more than one DMIs applications was made in one month period.
Most of the isolates of Sphaerotheca fuliginea from Saitama Prefecture showed high resistances to DMIs. However, the degree of resistance to triflumizole was less than to triadimefon and fenarimol. When DMI use was suspended, the a sensitivity of the fungus seemed to increase.
Three applications of triflumizole followed by two of quinomethionate showed excellent control of cucumber powdery mildew in a plastic house. Previously the performance of triadimefon in the plastic house was poor because of resistance and so DMIs were not used. Sensitivity to triadimefon seemed to be regained more than four years after the suspension of DMI use. On the other hand, sensitivity to triflumizole has decreased little over three successive years of trial use.
In 1991 a resistant strain of Sphaerotheca fuliginea to DMIs was found, for the first time, in Tokyo. Suspension or reduction of DMI application caused increased sensitivity in the cucumber fields where resistance to DMIs had occurred.
In 1991, a resistant strain of Sphaerotheca was found for the first time in Yamanashi Prefecture. There were some cases where the suspension of DMI applications caused increased sensitivity of the fungus, but non-DMI fungicides showed good performance to powdery mildew in the cucumber field in which DMi resistance had occurred.
Decreased sensitivity in Sphaerotheca fuliginea to DMIs was found in most of the cucumber fields investigated in Nagano Prefecture. The degree of resistance to triadimefon and fenarimol was rather high, and many isolates were more than 100 times less sensitive compared with the reference sensitive strain. A reduced number of DMI applications marginally increased sensitivity.
A resistant strain of Sphaerotheca fuliginea was found in most of the cucumber fields that were investigated in 1992 and 1993. Both sensitive and resistant strains were found in one field where DMI resistance was considered to be developing.
5種の土壌病原菌 Rhizoctonia solani AG4, Sclerotinia homoeocarpa, Fusarium oxysporum f. sp. lycopersici race2, Phytophthora capsici, Pythium aphanidermatum に対する精製木酢液剤の効果をPDA平板培地上で検討した。この結果, P. aphanidermatum で150倍, P. capsici で100倍, S. homoeocarpa で75倍, R. solani で50倍, F. oxysporum で30倍の各希釈濃度で菌糸生育阻止が認められた。また, P. capsici によるピーマン疫病及び R. solani によるホウレンソウ苗立枯病に対してはポット試験を, S. homoeocarpa による西洋シバダラースポット病に対しては圃場試験を行った結果, ピーマン疫病と西洋シバダラースポット病で発病抑制効果が認められた。
Damage to the stems and leaves of Jew's mallow Corchorus oltorius L. and leather leaf fern Rumohra adiantzformis (Forst. f.) Ching caused by slime molds occurred for the first time in Tokyo Metropolis in 1992-93. The fungi were identified, through their morphological characteristics, as Physarum gyrosum Rostafinski and Diderma effusum (Schweinitz) Morgan var. effusum.
Web blight of Hypericum calycinum, leaf blight of the Yarrows, Achillea millefolium and Asteriscus maritimus, sheath blight of Japanese iris, Iris ensata, and stem and root rot of Figmarigold, Lampranthus spectabilis, Pelargonium graveolens and Sultan snapweed, Impatiens wallerana, occurred in Tokyo Metropolis between 1991 and 1993. A Rhizoctonia species isolated from diseased plants was identified as Rhizoctonia solani Kühn. Inoculation tests showed that the fungus was the causal agent of these diseases.
Gray mold of Cyrtanthus, Cyrtanthus mackenii, Bouvardia, Bouvardia × hybrida and Evolvulus nuttalianus, occurred in Tokyo Metropolis in 1988, 1988 and 1993 respectively. The causal fungus isolated from diseased plants was identified as Botrytis cinerea Persoon by morphological observations and inoculation tests.
Southern blight of Japanese spurge, Pachysandra terminalis and Sweet box, Sarcococa ruscifolia, occurred in Tokyo Metropolis in 1993. The causal fungus isolated from diseased plants was identified as Sclerotium rolfsii Saccardo by morphological observations and inoculation tests.
Leaf spot of Amacrinum howardii Hort. occurred in Tokyo Metropolis in 1993. The causal fungus isolated from diseased plants was identified as a species of Phoma by morphological observations and inoculation tests.
The rust of spearmint, Mentha spicata L. and a cultivar of peppermint, M. piperita L. caused by Puccinia menthae Persoon was found in Tokyo Metropolis in 1992-93. Spearmint is a new host plant for the fungus in Japan. Mentha aquatica var. crispa and M. spicata var. crispa showed susceptibility to the rust by inoculations with its urediniospores.
Deterioration and damage to the leaves and stems of the ornamental plants, Spathiphyllum floribundum and Neoregelia sp., as a result of glebal attachment was observed at a greenhouse in Matsuo Town, Chiba Pref., Japan. These glebas were discharged from the fruit body of Sphaerobolus sp. which forms on the surface of the soil. Treatment of these fruiting bodies with validamycin liquid and by mixing mepronil dust with compost soil were effective in reducing glebal dispersion.
A virus, which showed the mosaic sympton, was isolated from Larkspur, Delphinium spp. in Chiba Prefecture in 1992. By using virus particle morphology, the reactions of several test plants, and serological tests, the isolate was identified as broad bean wilt virus.
Two viruses, which showed the mosaic sympton, were isolated from Marguerite, Chrysanthemum frutescens L., in Chiba Prefecture in 1992. For the identification of these viruses, samples were examined by means of mechanical inoculation of crude sap into several test plants, electron microscopic observation of infected leaves using the dip method, and serological tests. One of isolates was identified as cucumber mosaic virus and the other as chrysanthemum virus B.
茨城県つくば市の農業研究センター圃場で栽培されていたアルファルファに, 地際茎および主根基部が黒褐色に変じ腐敗する症状が発生した。病患部からはアルファルファとダイズの双方に病原性を有する糸状菌が高率に分離され, 形態的および生理的研究の結果, Calonectria crotariae (Loos) Bell et Sobers〔不完全時代: Cylindrocladium crotalariae (Loos) Bell et Sobers〕と同定された。本菌によるアルファルファの病害が観察されたのはこれが最初と考えられる。本菌による地際茎および主根基部の腐敗症状は, すでに報告されているアルファルファの黒あし病の1症状と考えられ, すでに報告されている Cylindrocladium floridanum に加え C. crotalariae を病原菌として新しく追加するよう提案する。