Benomyl resistant strains of Fusarium moniliforme, the causal fungus of “Bakanae” disease, were assayed using the Komada medium in place of PSA medium. Growth of mycelia on the Komada medium was slow and MIC value was lower than that on PSA medium. However, the method was able to evaluate Benomyl resistance on the Komada medium after 7 days of incubation. This method can be used for determining Benomyl resistance without the need for sterile operations.
In 1994 the major race of rice blast fungus isolated in Nagano Prefecture was 007. Other races isolated in this year were 001, 003, 041, 047, 101, 103 and 107.2. The appearances of the races 041 and 047, which were absent in 1980, were due to the increasing use of Yaekogane and Fukuhikari varieties of rice which have a resistance gene (Pi-z) to these races of rice blast.
To obtain the information about the effect of nitrogen application to rice plants on severity of blast disease epidemics, sporulation capacity of the disease lesions, a component of the epidemic, at various application timing was examined. Nitrogen topdressing applied from 9 days before to 4 days after infection of a blast fungus to rice plants increased the potential sporulating ability of the leaf lesions. The sporulating ratio of the lesions on treated/untreated rice plant is represented as y=-0.018t+1.88, where y is the ratio and t the infection time (days) after nitrogen topdressing, respectively.
The use of tractor is efficient in the control of rice blast in directly seeded paddy fields. Two new techniques which include the use of a tractor, to control of rice blast were investigated. In the first, granular fungicides were applied at the rate of 3kg ha-1 using tractor attached with a side dressing applicator, at the same time with the mechanical ridging operation in the stripe seeding type of directly seeded paddy fields. In this method, the fungicide is applied to the base of hills in the maximum tiller number stage. In the second, the tractor was fitted with a sprayer and liquid fungicide was applied at a rate of 300l ha-1 in both stripe and broadcast seeded paddy fields. The effect of applications of granular fungicides using the side dessing method was equal to that of paddy water applications of fungicide for leaf blast control. The effect of low volume spraying of liquid fungicide was equal to that of 1500l ha-1 application rates recently used. These results suggested that both methods are effective for efficient control of rice blast in directly seeded paddy fields.
Yearly fluctuation patterns of the occurrence of false smut in paddy fields in Ibaraki Prefecture were analyzed by Principal Component Analysis, using as variables the percentages of diseased plants in the 7 years from 1988 to 1994. The analysis showed that the first principal component was related to the disease abundance and the second to yearly fluctuation patterns. We classified the whole area of Ibaraki Prefecture into 8 different regions in which the patterns of yearly disease occurrence differed from each other based on the score values of the first and second components at each of 150 fields. These classifications will be invaluable for forecasting the occurrence of this disease.
In 1994, field surveys of viral diseases on green pepper plants were conducted at Kamisu, Ibaraki Prefecture. Infected leaves were collected from 15 locations, and the viruses were identified using both inoculation tests and morphological observations with an electron microscope. A total of three viruses was isolated. Tobacco mosaic virus (pepper strain) occurred in all locations, but cucumber mosaic virus (ordinary strain) and tomato spotted wilt virus (ordinary strain) occurred at only 3 and 2 locations, respectively.
Mycelial growth of the pathogenic fungi witches' broom, on Cupuacu trees were inhibited when treated with Folicur (active component-Tebuconazole) and Bayfidan (active component-Triadimenole) at 1ppm on PDA medium. Spore dispersal from basidiocarps and germination of basidiospores were greatly inhibited when basidiocarps on dead branches infected with the disease were sprayed with Befran liquid×1000, Folicur emulsion×1000, Bayfidan W. P.×1000 and Berkute W. P.×500.
Eight fungicides were applied to dead branches of Cupuacu trees infected by the pathogenic fungi witches' broom, Crinipellis perniciosa. The results showed that in all cases formation of basidiocarps on the dead branches were inhibited when sprayed at 1 to 4 week intervals.
In order to control witches' broom in Cupuacu trees an experiment was conducted to assess the effect of spraying seedlings with Folicur emulsion ×2, 000 and Bayfidan W. P. ×1, 000 at 2, 4 and 6 weeks intervals. The growth in Cupuacu seedlings was inhibited when sprayed with Folicur ×2, 000 at an interval of 2 weeks. Spraying at 4, 6 weeks intervals with both Folicur ×2, 000 and Bayfidan ×1, 000 were judged to be of practical use because good control effects were achieved including inhibition of basidiocarps formation on dead branches and the growth of Cupuacu seedlings wes not inhibited.
Gray mold of Angelica keiskei Koidz, Jew's Mallow Corchorus oltorius L., Sweet basil Ocimum basilicum L., Amazon lily Eucharis grandiflora Planch et Linden, Spathiphyllum cannifolium Schott, Sweet scabious Scabiosa atropurpurea L., Christmas-tree kalanchoe Kalanchoe laciniata (L.) DC., Nematanthus gregarius D. L. Denh and Canary ivy Hedera canariensis Willd. occurred in Tokyo Metropolis between 1989 and 1994. The causal fungus which was isolated from diseased plants was identified as Botrytis cinerea Persoon by morphological observations and inoculation tests.
Leaf spot of Angelica keiskei Koidz. occurred in Tokyo Metropolis in 1994 and 1995. The causal fungi, which were isolated from diseased plants, were identified as Septoria dearnessii Ell. et Ev. and a species of Septoria by morphological observations and inoculation tests.
Stem blight and leaf spot of Vinca minor L. occurred in Tokyo Metropolis in 1992. The causal fungus isolated from diseased plants was identified as Phoma exigua Desmaz. var. inoxydabilis Boerema and Vegh apud Vegh et al. by morphological observations, inoculation tests and colour reaction test with NaOH. This is first report of a disease of V. minor being caused by P. exigua var. inoxydabilis in Japan.
Damping-off of Jew's mallow Corchorus oltorius L., fairy primrose Primula malacoides Franch. and Roebelen date palm Phoenix humilis Royle var. loureirii Becc. occurred in Tokyo Metropolis. The fungus isolated from diseased plants was identified as Rhizoctonia solani Kühn and inoculation tests showed that this was the causal agent of the disease.
Web-Blight of Monterey Cypress, Cupressus macrocarpa, occurred in Tokyo Metropolis in 1994. A Rhizoctonia species isolated from diseased plants was identified as R. solani AG-1. Inoculation experiments showed that the fungus was the causal agent of the disease.
From 1992 symptoms of Rhizoctonia rot and southern blight of Sandersonia aurantiaca Hook. were observed in Chiba Prefecture. Rhizoctonia solani AG-2-2 and Sclerotium rolfsii, isolated from infected roots, basal stems and rhizomes, were demonstrated as the causal agents of the diseases by inoculation tests. An experiment for the chemical control of Rhizoctonia rot was conducted. The results showed that dipping of rhizomes into Tolclofos-methyl solution was effective.
Southern blight of Christmas bells, Sandersonia aurantiaca Hook. and Atractylodes ovata D. C. occurred in Tokyo Metropolis in 1993. The causal fungus which was isolated from diseased plants was identified as Sclerotium rolfsii Saccardo by morphological observations and inoculation tests.
Experiments were conducted to test the effectiveness of low volume applications of hightly concentrated oxine-copper WP in the control of Typhula snow blight on turf grass at golf courses in Nagano Prefecture. An application of 0.1ml m-2 of the fungicide diluted 40× was more effective in the control of this disease than that of the commonly used volume and concentration of 0.5ml m-2 and diluted 200×.
Three experiments were conducted to assess the sensitivity of injured or non-injured black-pepper to the Fusarium pathogen. Firstly, attempts were made to infect non injured seedlings root at their tips or in their mid-portion. Secondly, injured and non injured sites at seedling stem bases were infected. Finally, for older plants cut branches, differing in age, were infected at the site of the wound. In experiments one and two, all plants died, indicating that they are very susceptible to Fusarium regarding of the infection site. In experiment three old and young branches did not differ in their sensitivities to the fungi.
An greenhouse experiment was performed to assess the relationship between Fusarium spore densities in the soil and infection rate of black-pepper seedlings. Mata soil (a forest soil of the Amazon) were inoculated with spore suspension increasing concentration from 2.7×102 to 5.4×105 spores 1g soil. There was a positive correlation between the concentration of spores in soil and infection rates of the seedlings.
A greenhouse experiment was conducted to evaluate the infection rate of black-pepper seedlings when grown in five soil types infected with Fusarium at a rate of 5×104 spores g-1 soil when planted in “Mata” and “Barro” soil the infection rates were 22% and 28%, respectively. However, in Tome-Açu, Varzea, or Santa-Izabel the infection rates were much higher at 92%, 78% and 50%, respectively.