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We investigated the population structure of the rice blast fungus prevalent in Akita Prefecture in 2000 and 2002 using Pot 2 rep-PCR DNA fingerprinting. Three hundred twenty-five isolates were obtained from 43 districts of the prefecture. All of the isolates, except two (race 003) obtained in 2000, belonged to race 007 and were classified into 39 genotypes using Pot 2 rep-PCR DNA fingerprinting. Four of the genotypes were identical to those of Miyagi isolates. At the 80% similarity level, Akita and Miyagi isolates were divided into nine groups (I-IX). Approximately 80% of them fell into two major groups, VI and VII. These groups appeared to be widely distributed in Akita Prefecture. The results suggest that the population structure of rice blast fungus in Akita Prefecture, determined using Pot 2 rep-PCR DNA fingerprinting, is fairly simple.

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We investigated the optimal application timing of simeconazole (2-(4-fluorophenyl)-1-(1H-1, 2, 4-triazol-1-yl)-3-trimethylsilylpropan-2-ol) as a rice false smut control fungicide using the formulations of simeconazole 20% wettable powder and 1.5% granules. The treatments at 1-2 and 2-3 weeks, respectively, before heading were the most effective treatments in a field test. These periods overlap the optimal application timing of simeconazole for controlling rice sheath blight. Consequently, we consider that the treatment with simeconazole can be used to control both false smut and sheath blight simultaneously.

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Effects of Soil Adsorption on Uptake of Simeconazole by Rice Plants and Sheath Blight Control Effect Mikio TSUDA and Shigehiro KATO The purpose of this study is to investigate the significance of soil adsorption on the uptake of Simeconazole (2-(4-fluorophenyl)-1-(1 H-1, 2, 4-triazol-1-y 1)-3-trimethylsilylpropan-2-ol) by rice plants and the control effect on sheath blight. Correlation analysis of adsorption coefficient (Kd) values and different soil physicochemical parameters revealed that the soil adsorption of simeconazole did not correlate to soil pH, cation exchange capacity, organic carbon or clay mineral content. Simeconazole was detected in rice plants three days after its submerged application, and progressively increased within 6-9 days. However, there was a tendency for the uptake of simeconazole by plants to be delayed in soils of high Kd values. In disease control activity tests, simeconazole showed excellent efficacy against rice sheath blight in all soils tested.

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The effects of temperature on Wheat yellow mosaic virus (WYMV) propagation and symptom development in wheat plants were investigated under both field and growth chamber conditions. Throughout the 5-year investigation using a WYMV-infested field, disease incidences varied, but disease progression patterns were similar among the years of investigation. Disease incidences and severities increased when the daily mean air temperature (DMAT) was approximately 5°C, and decreased by masking when the DMAT was above 10°C. Under growth chamber conditions, when wheat plants were mechanically inoculated with WYMV and grown under controlled environmental conditions at 5, 10 and 15°C, the latent periods for symptom development and virus detection were shorter at 10°C than at 5°C. The symptoms rapidly disappeared at 10°C, while they appeared gradually at 5°C, but were more severe than those at 10°C. No symptoms appeared at 15°C. These results show that air temperature differentially affects WYMV development and expression: the optimal temperature for symptom development is approximately 5°C, while the optimal temperature for virus propagation is approximately 10°C.

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An undescribed disease was observed in Malabar nightshade (Basella rubra L.) in Miyagi Prefecture in 1996. Diseased plants showed large spots lesions with purple halos on leaves and stems. A pathogenic fungus was isolated from the diseased plants, and the leaf spot symptoms were observed in inoculated host plants. The fungus was identified as Fusarium proliferatum on the basis of morphological and cultural characteristics. To our knowledge, this is the first report on the occurrence of the purple spot in Malabar nightshade in Japan

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Since 2001, root rot of grafted cucumber (Cucumis sativus L) caused by Phomopsis sp. has been observed in open-field cultivation in Fukushima, Japan. Symptoms, such as wilting of the plants, were first observed in early August. A difference in susceptibility was observed among rootstock varieties (Cucurbita spp.) when seedlings were grown in infested soil. To our knowledge, this is the first report on the occurrence of root rot in open-field-cultivated cucumber in Fukushima.

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In 1999, a potyvirus was detected in Lilium × formolongi plants showing mosaic symptoms in Akita Prefecture, Japan. The virus was confirmed to be the causal agent of the disease by sap inoculation tests, but did not infect Chenopodium quinoa, Nicotiana benthamiana, N. clevelandii and Tetragonia tetragonoides. The amino acid sequence of its coat protein (CP) was revealed to have a high homology (98. 5-91. 3%) with those of isolates reported as Lily mottle virus and Tulip band breaking virus (TBBV). Although these isolates and the present virus could be subdivided into two groups on the basis of the number and the sequence of their CP amino acids, the two groups did not correspond to the two virus species. These findings show the need of further investigation and discussion on the taxonomic status of a tentative species TBBV.

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An undescribed disease of giant onion (Allium giganteum Regel) was observed in Miyagi Prefecture in 1999. Disease symptoms appeared mainly on leaves and sheaths, and these symptoms were elliptical brown to purple lesions, becoming zonate with the development of the disease. Pathogenicity to the host plant was demonstrated by the inoculation of a fungus isolated from a diseased plant. The fungus was identified as Alternaria porri on the basis of morphological and cultural characteristics. To our knowledge, this is the first report on the occurrence of purple blotch in giant onion in Japan.

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A release experiment of the European tarnished plant bug, Lygus rugulipennis, adults to immature pods of adzuki bean (Vigna angularis) in several pod growth stages was carried out. The results obtained show that the type of seed injury depends on the growth stage of the pods infested: pods that had just completed lengthening dropped before maturity ; young seeds in completely lengthened pods shriveled or developed stinging marks on their coats; more mature seeds developed stinging marks on their coats. The results of another release experiment of bug nymphs show that the nymphs can also cause the same types of seed injury as those caused by the adults. The degree of the injury caused by 5th instar nymphs is higher than those caused by the 3rd and 4th instar nymphs.

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Ovipositional preferences of Helicoverpa assulta and Helicoverpa armigera femalesfor several host plants were investigated. Among the five host plants tested, the H. assulta female showed a strong ovipositional preference for tobacco only. On the other hand, the H. armigera female showed a weak ovipositonal preference for the five host plants tested, but the net which covered the insect rearing cage had a significantly (p <0.05) greater number of eggs. This suggests that the H. armigera female exhibits a unique characteristic, that is, it oviposites anywhere else than the host plants.

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Attractions of the nontarget noctuids, Orthosia ella and Ochropleura plecta, to the purchasable lure using the sex pheromone of the cabbage armyworm, Mamestra brassicae, which contains (Z)-11-hexadecenyl acetate (Z 11-16Ac), (Z)-11-hexadecenal (Z 11-16Ald), (Z)-11-octadecenyl acetate (Z 11-18 Ac), (Z)-9-hexadecenyl acetate (Z 9-16Ac), and n-tetradecyl acetate (14Ac) in a ratio of 100: 0.1: 2: 0.5: 0.5, were investigated. O. ella males were attracted to Z11-16Ac alone and a mixture of Zl l-16Ac and Z11-16Ald in a ratio of 100: 0.1, but not to those in ratios of 100: more than 0.3. The addition of 14Ac to these components reduced the attraction activity in some degree. O. plecta males were attracted to Z11-16Ac alone and the mixtures of Z11-16Ac and Z11-16Ald in ratios of 100: 0.1-3, particularly more males were attracted to those in ratios of 100: 0.3-1. The addition of Z11-18Ac to these two components made clear the effect of the ratios of these components. The addition of Z 9-16Ac to these components reduced the attraction activity in some degree. Because more M. brassicae males were attracted to mixtures of Z11-16Ac and Z11-16Ald in ratios of 100: 0.1-0.3 than Z11-16Ac alone and other ratio mixtures of those, it is considered that the addition of 0.3% Z1 l-16Ald to Z11-16Ac is suitable method for the suppression of the attraction of O. ella; however, the addition of a disruptant may be needed for that of O. plecta.

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In Hokkaido, petioles of Japanese butterbur, Petasites japonicus, are heavily injured by some syrphid larvae, whose specific names are unclear. In this study, I clarified the biology of two species of Cheilosia in butterbur in Hokkaido. Young larvae of both species attack the inner side of petiole from May to July, and then mature larvae bore downward to the subterranean stalk. C. yesonica was dominant in the edibie petiole and was likely to be univoltine, whereas C. fluvipes was bivoltine. Both species overwintered in the pupal stage in the shallow soil near injured butterburs, and emerged in spring. They could be distinguished by the shape and the number of spiracular openings of the posterior respiratory process in mature larvae or pupae.

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Swelled seeds of summer cypress, Kochia scoparia, are edible and highly prized for “field caviare” in northern Japan. However, insect feeding on summer cypress has not been assessed yet. We surveyed the insect fauna of summer cypress on late September 2002, in Morioka City (39.7°K N, 141.2°K E). Six pest species, i. e., the sugarbeet leaf bug, Orthotylus (Melanotrichus) flavosparsus, the black aphid, Aphis rumicis, the beet webworm, Hymenia recurvalis, the mugwort looper, Ascotis selenaria, the Dewick's plusia, Macdunnoughia confusa, and the mulberry caterpillar, Sarcopolia illoba, were recorded. Among these species, H. recurvalis and S. illoba, both of which fed on the seeds vigorously, seemed to be the most important pest species.

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Species and their seasonal attractant prevalence were monitored by a synthetic pheromone trap of the oriental fruit moth, Graphorita molesta, from 1982 to 1984 in central Hokkaido. G. molesta adults were not captured by the pheromone trap in each point for each year. In contrast, the male adults of G. tenebrosana, G. dimorpha, Pammene nemorosa and Cnephasia cinereipalpana were captured by the pheromone trap of G. molesta. These species may utilize same-sex pheromone components. G. tenebrosana showed the first peak in mid-June, but the number of generations was not clear. G. dimorpha adults were not captured in large numbers by the pheromone trap. P. nemorosa showed two peaks from early to mid-June and mid-August. C. cinereipalpana adults were captured from mid-June to mid-August.

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