ANNUAL REPORT OF THE SOCIETY OF PLANT PROTECTION OF NORTH JAPAN

The Ascochyta leaf spot diseases of adzuki bean, Kidney bean, Spanish runner bean, lima bean, soybean, eggplant, tomato and potato in Hokkaido are reported. The fungus on each host was shown to be morphologically and pathologically identical. In cross inoculation studies, symptoms produced on each host were similar and adzuki beanwas most severely infected, irrespective of the original source of the inoculum. Ascochyta sojaecola Abramoff, A. melongenae Takimoto and A. lycopersici Brun. are considered as synonyms of A. phaseolorum Sacc., which has priority as the earliest named species.

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In Tohoku district, there have been known to occur several major pest insects of the soybean seed, among which the soybean pod borer, Leguminivora glycinivorella Mats., is the principal pest in cooler northern region, and others including stink bugs, Nezara antennata Scott, Riptortus clavatus Thunb., etc., the pod gall midge, Asphondylia sp., and the bean pod worm, Matsumuraeses phaseoli Mats., are much more harmful in warmer southern region of the district. Motoyoshi province, Miyagi prefecture, is a transitional zone between the cooler and the warmer regions defined above, and nearly all of major pests known from the district were found abundantly in this province. In such areas, therefore, it is desirable to find out simultaneous control measure against the seed pests complex mentioned above.
From this point of view, a field experiment was performed in 1972 in Motoyoshi province to make clear the effective timing of twice applications of bycid dust in 3 kg per 10 a. for simultaneous control of major soybean pest insects. The results indicated that the first application should be made just after or less than one week after the full bloom and the second at about four weeks after the full bloom of soybean. This timing of insecticidal applications may be adaptable for mid-and late-varieties of the soybean, such as “Miyagi-shirome” and “Raiden”.

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Since 1970 at a field in Nopporo, Hokkaido, the potato has been severely damaged by the wireworm. In 1971 and 1972, field experiments were undertaken to evaluate the effect of several insecticides for controlling the wireworm. The results of laboratory experiment in 1970 were reported previously (Ohashi et al. 1972, Ann. Rept. Plant prot. North Japan). In 1971 and 1972 a fixed amount of insecticides were applied into the soil. The number of sound potatoes was counted in September in 1971 and August in 1972. From the results obtained above experiments, it was concluded that application of 6 kg of Heptachlor dust (2.5%) or PHC dust (1%) par 10a, just before the sowing of potato, is substantially effective.

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At Midagahara, Mt. Gassan (about 1, 400 m above sea level), Yamagata prefecture, a light trap survey of moths had been made from 23rd to 27th July, 1971. On 24th July, northwest wind of about 5 to 6m/sec. blew over this plateau, and at this night Agrotis ypsilon HUFNAGEL, Euxoa sibirica BOISDUVAL and a few other moths were attracted to the light. A. ypsilon found at this night was very active and not alighted on a white screen for collecting. Moreover, many moths passed over the collecting site on the air current. About twenty specimens among them were caught by an insect net with elongate stick, and most of these were A. ypsilon. At other nights, particularly on 25th July, A. ypsilon had not been collected, despite the fact that many other moths were attracted to the light. From these facts, it seems highly probable that A. ypsilon migrated in a mass at night on 24th July across Midagahara. Another interesting fact is that E. sibirica with seasonal migratory behaviour was also found only on 24th July.
From light trap records and sampling in a soy-bean field severely infested by A. ypsilon, it was confirmed that the adults occurred abundantly in mid July, 1971, on the plain in ShOnai district west to Mt. Gassan. Although the occurrence of adults on the plain nearly agrees with the migration observed of high land in time, the original source of migrating adults is open to question. In 1972, ovaries of the female adults caught by a light trap on the plain were examined. A large part of females had developed ovaries from May to July, while those caught after August had undeveloped ones. This result well agrees with a previous records obtained in Iwate prefecture (Chiba, 1972).
In relation to these findings, some problems in migration and mass outbreaks of A. ypsilon were discussed.

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