[in Japanese]

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Over 1000 rice varieties and breeding lines have been screened for resistance to rice waika disease, a semipersistent leafhopper-borne virus, in fields and a greenhouse from 1973 to 1977. In field tests, varietal resistance in terms of percent infection showed variation from 0 to 100%, however, the virus recovery test and the virus inoculation test (strain S) indicated that most of the varieties were classified either resistant or susceptible group. Donors of the resistant gene in japonica were Aichi-asahi, Saikai No. 115, Aikoku and Shinriki. The former two varieties were highly resistant and the latter were moderately resistant.

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Nephotettix cincticeps adults were confined to infected source rice plants by cages for a 24-h acquisition access period at 25°C. Immediately after the acquisition, the insects were placed one couple per rice seedling at the 2-leaf stage in a test tube for a 24-h inoculation access period at 25°C. The inoculated seedlings were grown in pots for disease development. Based on the percentage of diseased plants, 3 of 13 varieties tested with 3 replicates were determined to be moderately resistant and others were susceptible to the virus. No resistant varieties were detected. The height of diseased plants was reduced in all of the varieties.

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[in Japanese]

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Causal fungi of onion leaf blight collected from the onion growing areas in Saga prefecture were as follws: Botrytis squamosa WALKER, Botrytis cinerea PERSOON and Pleospora herbarum (Fr.) RABENHARST (conidial stage, Stemphylium botryosum WALL-ROTH). Perithecia of P. herbarum were dark browh, glabrous, slightly flattened, 158-350×126-441μ. Asci were hyaline, short clavate, 8-spored, 26-34×103-155μ. Ascospores were dark brown, not flattened, straw rice-bag like shape having longitudinal and cross septa, 13-16×27-34μ. This fungus was newly found as one of the causal fungi of onion leaf blight in Kyushu.

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[in Japanese]

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[in Japanese]

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The effects of fungicides were examined for the bacterial rot of lettuce caused by Pseudomonas sp.. Streptomicin, copper wettable powders (copper oxychloride, copper sulfate, basic and copper dihydroxide), and polycarbamate were screened out of twenty three fungicides used in the paper disk method. Streptomycin showed significant effect in the case of single needle inoculation, and the effect of polycarbamate was observed in the case of spray inoculation. In field test, polycarbamate showed significant effect while the effect of copper wettable powder was not observed and its chemical injury on petioles occurred.

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[in Japanese]

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The population densities of larvae and adults of the rice leaf roller, Cnaphalocrocis medinalis GUENÉE, were investigated by a direct observation in the experimental paddy fields at Chikugo, northern Kyushu. In the field of early-planting culture, young instar larvae began to appear at the end of June and the larval density of the 4th and 5th instars reached 0.75 per hill in early July. Thereafter, the density was very low level until harvest. In the field of normal season culture, the larvae were observed from mid-July and their population densities of the 4th and 5th instars increased gradually, reach-ing a maximum of 0.23 per hill at the end of August. The larval density decreased gradually from early September and only a few larvae were found just before harvest, early November. It seemed that the generations overlapped each other later than August, since various instars of the larvae were observed in a field at the same time. There were distinct peaks of adults occurrence : one peak in early-planting culture in mid-July and two in normal season culture in early August and late September. Two hymenopterous parasites were observed infesting larvae of the pest. The highest percentage parasitism of Trathala flavo-orbitalis was 30.3 % in early-planting culture in early July, while that of Apanteles sp. was 12.5 % in normal season culture at the end of August.

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[in Japanese]

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Pesticide residues in water were monitored at six sites of creeks in Saga in 1977. Residue levels corresponded to the application time and dosages of pesticides applied in paddy fields. Herbicide benthiocarb was found in a range of 2-7 ppb in average concentration throughout the growing period of rice plants, showing higher concentration during the former growing period, but CNP and NIP were considerably lower. Carbamate insecticides MTMC and XMC were found in a range of 0.1-0.6 ppb in average concentration, but BPMC was detected with less frequencies.

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Field tests were conducted using two varieties of potato, Tachibana and Shimabara. Tachibana is moderately resistant to the virus Y and susceptible to the leafroll virus; Shimabara is susceptible to the virus Y but resistant to the leafroll virus. On Tachibana, the occurrence of aphids during the early stage of potato was prevented by mulching with silver polyethylene film but not with clear polyethylene film. The incidence of the mosaic in the plants of next crop was significantly reduced by mulching with both films. Mulching with clear polyethylene film advanced the growth of potato. This was the reason why the incidence of the virus Y mosaic was remarkably reduced whereas mulching with clear polyethylene film gave no effects against the aphids. The incidence of the leafroll in the plants of next crop was reduced to some extent by silver polyethylene film but remarkably by three applications of insecticide (acephate WP) at weekly intervals during the early stage of potato. The first two times of insecticide applications could be replaced by mulching with silver polyethylene film for control of the leafroll. On Shimabara, the incidence of the mosaic in the plants of next crop was affected by neither of the films. The reason for the ineffectiveness is uncertain.

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[in Japanese]

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The effect of sugar solution fed at adult stage on mating was studied on Leucania separata WALKER and Agrotis ipsilon HUFNAGEL in the laboratory maintained at 25°C. Adults used were obtained either from mature larvae and pupae collected in the field or from larvae reared in the laboratory. A couple of moths were held in earthen or plastic cages containing a vial of either 10 per cent sugar solution or water alone for food. Each female was dissected after death for the determination of the presence of spermatophores as proof of its successful mating. Both species showed two different cases on their matinigs: first, the intake of sugar was essential for the success in mating and, second, the intake of sugar was not essential. When adults could mate without sugar, the weight of the pupae was larger, the fecundity was higher, and the adult life-span was longer compared with the adults which could not mate without sugar. The fact suggests that the above two cases are likely to be caused by the nutritional state during larval stage. When larvae are forced to feed on unfavourable foods, the resultant moths are probably unable to mate without sugar.

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A laboratory experiment was conducted to determine whether the characters of the black cutworm, Agrotis ipsilon, are affected by larval density. The larvae were reared at densities of 1, 2, 3, 5, 10 and 30 individuals per vessel at 25°C and a 16 : 8h light : dark cycle. The rate of larval and pupal development, the length of preoviposition period and longevity of the male moths were not affected by the density during larval period. The weight of pupae, fecundity and longevity of the female moths were, however, reduced when the larvae were reared at high density. The mortality prior to the 5th moult was low, and the increased mortality in crowded culture occurred mainly between the last larval instar and pupal stage. The aggressive behaviour of the mature larvae was a major factor affecting the density-dependent mortality.

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The adults of Thysanoplusia intermixta (WARREN), visiting the flowers of Abelia grandiflora REHD. were collected in Fukuoka, and from these adults the eggs were prepared. The eggs, larvae and pupae were reared in incubators at 18, 20, 25 and 30°C. From the relationships between temperature and developmental velocity, the threshold of the development and thermal constant for completion of immature stages were calculated as 7.0°C and 580-625 day-degrees, respectively. From the seasonal prevalence of the adult emergence and the egg densities, four generations were recognized from June to October. In addition to these generations, the adult emergence of the overwintering generation was estimated in the period from April to early May in Fukuoka. The adult population densities were highest in the 1st and 2nd generations, and lowest in the 3rd generation.

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The cabbage moth, Mamestra brassicae L., is a polycyclic species with facultative diapause in the pupal stage. The lower threshold temperature for the development of hibernating pupae was 8°C. The sum of effective temperatures above 8°C, calculated from December 21 to the peak of moth appearance recorded by a light trap in spring, was 239.1 ± 34.9 (SD) day-degrees (°C). The emergence of non-diapaused and summer-diapaused pupae occurred when the averaged 5-day temperature reached 20-24°C. There was a significant correlation (r=0.896) between the duration of summer diapause and the sum of effective temperatures above 24°C. The fact indicates that summer diapause in the pupal stage lasts during the period of averaged 5-day temperature of above 24°C prevailed. The difference in temperature conditions among different altitudes affects the duration of summer diapause and subsequent times of adult emergence in autumn in a district.

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