Two hundred fifty isolates of Pyricularia grisea were collected from rice plants in Kanto-Tokai district in 1994. Fourteen pathogenic races were identified based on 12 Japanese differential varieties. Race 007 was dominant in Tochigi, Gunma, Saitama, Chiba, Nagano, and Shizuoka Prefectures, whereas race 001 was dominant in Mie and Kanagawa Prefectures. We observed a significant change from 003 to 007 in pathogenic race composition as compared to the survey in 1976 and 1980 except for Mie Prefecture.
The population of Pseudomonas glumae on brown rice washed by distilled water was examined. The population of P. glumae on brown rice slightly decreased compared to that of P. glumae on rice grains. Brown rice was shaken using distilled water for 30mins (115rpm/min) at 25°C. This cleaning method was effective to reduce the population of P. glumae on brown rice apparently. These results suggest that the washed brown rice is applicable as pathogen-free rice seeds.
In the autumn of 1995, a powdery mildew fungus was observed on Angelica keiskei cultivated at Izu Oshima Island, Tokyo, Japan. The leaves, petals of the flower and stems of the plant were covered with amphigenous colonies and persistent mycelium. Conidiophores were straight, 89-159μm in length, and 10-16μm in width. Foot-cells were cylindric, 27-48μm in length, and 8-10μm in width. Conidia were cylindric (-ellipsoid) to oblong, produced singly, and measured (29-)33-46(-52)×13-20μm. The length/width ratio of conidia were between 2.31 to 2.39. Appressoria of conidial germ tubes were lobed, Erysiphe polygoni type proposed by Hirata (1942, 1955). From inoculation experiments of the fungus, we recognized that the fungus on Angelica keiskei was pathogenic to the host plant. Since the cleistothecia of the fungus were not present, we proposed that the fungus was Oidium sp. belonged in E. polygoni type. This is the first report of powdery mildew on cultivated Angelica keiskei.
Dazomet combined with soil solarization showed a superior control of tomato bacterial wilt to methyl bromide. One month after the treatment, the residue of dazomet in the soil was reduced to 0.2% of that immediately after treatment, which was almost the same at transplanting time of tomato seedlings. The results suggested that dazomet combined with soil solarization could decrease the phytotoxicity by the residue of dazomet and the number of times of removing the gas from the soil.
From 1994 to 1966, monitoring sensitivity to diethofencarb mixtures (diethofencarb+thiophanate-methyl and diethofencarb+procymidone) was undertaken on 2, 519 isolates of Botrytis cinerea collected from 208 fields of cucumber, tomato and other crops in Kanto-Tosan district. The result revealed that resistant strains to diethofencarb mixtures were distributed widely in this district. The frequency of the resistant strain increased year by year and reached 60% of all isolates. However, most of the resistant strains were benzimidazole highly resistant and diethofencarb weakly resistant (HR·WR). The high frequency of the resistant strain was observed in the fields where diethofencarb mixtures had been used intensively.
A fungicide sensitivity of Botrytis cinerea could easily be detected by picking up conidia formed on a lesion of a diseased tomato with the tip of a toothpick and by inoculating on to a fungicide amended selective medium for B. cinerea followed by incubation under the room temperature or 2°C for 3 or 4 days. It seemed that the sensitivity of the fungus with this rapid and simple test could be determined by anyone because there is almost no cross contamination.
Monitoring sensitivity from 1994 to 1995 revealed that resistant strains to diethofencarb mixtures occurred extensively in the population of Botrytis cinerea on several vegetables and flowers in Tochigi Prefecture.
In 1994, a resistant strain of Botrytis cinerea to diethofencarb mixtures was found for the first time in Gunma Prefecture. From 1994 to 1996, resistant strains to diethofencarb mixtures on cucumber spread throughout the area year after year.
A rapid sensitivity test using a toothpick was employed to detect resistant strains to benzimidazole, dicarboximide and diethofencarb in B. cinerea on tomato in Futtsu, Chiba Pref., Japan. The test constituted of the following: picking up of conidia from one single lesion of a diseased fruit of tomato with a toothpick, inoculating the conidia on to a fungicide amended selective medium for B. cinerea and observation of colony formation on the medium to determine fungicide sensitivity of the isolate. Of all isolates derived from 130 lesions, sensitivity of eighty five isolates (65.4%) could be determined. The most frequent phenotype of sensitivity was benzimidazole-resistant, dicarboximide-resistant and diethofencarb-sensitive (RRS) and its frequency, was 60.0% of all solates. On the other hand, the frequency of the phenotype resistant to all these fungicide (RRR) was the least, 1.2%. No clear correlation was observed between fungicide sensitivity of isolates and fungicide use on the field where the isolates were collected.
Sensitivity to diethofencarb mixtures was monitored in 623 isolates of Botrytis cinerea collected from thirty four tomato fields in Tokyo from 1994 to 1996. Through the monitoring, resistant strains to diethofencarb mixtures were found for the first time in Tokyo. In 1996, the frequency of the resistant strain increased to 53.2% of all isolates and the phenotype which is highly resistant to benzimidazole and weakly resistant to diethofencarb (HR·WR) was the most dominant, 71.8% in all resistant strains.
Fungicide sensitivity of Botrytis cinerea was monitored with a rapid sensitivity test, using toothpick on protected fruit vegetables in Kanagawa Prefecture. Although a strain of the fungus, which was resistant to both diethofencarb-benzimidazole mixture and diethofencarb-dicarboximide mixture, was frequently detected on tomato and cucumber in 1995, the frequency of the resistant strain was reduced in 1996. On the other hand, a resistant strain to dicarboximide was the most frequently detected on strawberry. The rapid sensitivity test used in this surveillance was laborsaving, reliable and expected to be used widely in practical fields.
Monitoring sensitivity to benzimidazoles, dicarboximides and diethofencarb was conducted in 365 isolates of B. cinerea collected from 31 protected cucumber fields and 28 open vineyard in Yamanashi Prefecture from 1994 to 1996. On cucumber, frequency of resistant strain to diethofencarb mixture was as high as 50%, and one third of them was highly resistant to diethofencarb. On the other hand, only a few resistant strains to diethofencarb mixture were detected in the population of the fungus on grapevine.
Monitoring sensitivity from 1994 to 1996 revealed that a multiple resistant strain to benzimidazoles, dicarboximides and diethofencarb was distributed extensively in the population of Botrytis cinerea in tomato fields. An effective countermeasure should be constructed to control the resistant strain.
Ascospore discharge pattern of Venturia inaequalis was monitored using a 7-day-recording spore trap for 4 years. Each year, ascospores were trapped mainly at day time during wet intervals initiated by rain. The ascospore discharge pattern of the pathogen monitored in this study resembled that of the one in Ontario, in eastern Canada in 1991.
Three viruses, alstroemeria mosaic virus, an unidentified potyvirus and cucumber mosaic virus, were detected from Alstroemeria hybrid plants showing mosaic and white streak symptoms in Chiba Prefecture in 1995 and 1996.
Leaf Blight of Lewisia cotyledon occurred in Saitama Prefecture in 1995. The causal fungus isolated from diseased plant was identified as Bipolaris sp. by morphological observations and inoculation tests.
Leaf spot of drummond phlox Phlox drummondii Hook. occurred in Tokyo Metropolis in 1996. The causal fungus isolated from diseased plants was identified as Stemphylium botryosum Wallroth by morphological observations and inoculation tests. This is the first report on the disease in Japan.
Anthracnose of Amacrinum howardii Hort., winter-flowering begonias Begonia×hiemalis Fotsch and Japanese chinquapin Castanopsis cuspidata var. sieboldii (Makino) Nakai occurred in Tokyo Metropolis in 1996. The causal fungus isolated from the diseased plants was identified as Colletotrichum acutatum Simmonds ex Simmonds by morphological observations and inoculation tests. This is the first report on anthracnose of A. howardii, begonias and Japanese chinquapin caused by C. acutatum in Japan.
Leaf spot of strawberry saxifraga Saxifraga stolonifera Meerb. occurred in Tokyo Metropolis in 1996. The causal fungus isolated from the diseased plants was identified as Phoma exigua Desmazières by morphological observations and inoculation tests. This is the first report on the disease in Japan.
Leaf blight of Chinese lantern plant Pysalis alkekengi L. var. franchetii Mark. and stem and root rot of poinsettia Euphorbia pulcherrima Willd. occurred in Tokyo Metropolis in 1996. The causal fungus isolated from the diseased plants was identified as Rhizoctonia solani Kühn by morphological observations and inoculation tests. This is the first report on the diseases in Japan.
The toxicity of four kinds of insecticide solution, Imidacloprid, Buprofezin, Cartap and MEP on eggs, larvae, prepupae and pupae of Trichogramma japonicum was studied in laboratory. The result suggested that all of the insecticides tested could penetrate into the egg shell of the host and showed different degree of toxicity on wasps. In dipping method, the toxicity of Imidacloprid and Buprofezin was lower than that of other insecticides. The toxicity of Cartap and MEP was relatively higher on the Trichogramma. When Stages of wasp pupae and larvae were treated with MEP, emerged adults died before laying eggs. When prepupal stages were treated with MEP, the treated-generation adult could survive for one day but 80% of the female adults could not oviposit. When stages of wasp eggs were dipped into MEP, the treated-generation adult could oviposit in spite of decreased number of oviposited eggs.
Effects of three insecticides, Imidacloprid, Buprofezin, and MEP on the population increase of the treated generation and the next generation of Trichogramma japonicum were investigated by the life table method. By dipping method into practical concentration, the toxicity of Imidacloprid and Buprofezin was lower than MEP; that is, the Trichogramma adult of the treated-generation could oviposit, the fecundity, net reproduction rate [Ro], innate capacity for increase [rm] of the treated generation and of the next generation had no significant difference from check. The toxicity of MEP was relatively higher on the wasp. When the prepupae were treated with MEP, the [rm] of the treated generation became negative. When the eggs treated with the said chemical, the fecundity of the treated generation adults was significantly lower than that of check. But the values of the population increase parameter in the next generation recovered to the level of the untreated population.