Barley yellow dwarf virus (BYDV), occurring in Kyushu, was purified and the antiserum against BYDV was prepared. The antiserum reacted with BYDV up to a dilution of 1/160 in precipitin ring interface test. Using this antiserum, the serological diagnosis of BYDV by ELISA was developed. BYDV in the leaf extract of infected barley plants cpuld be detected up to a dilution of 1/640 by ELISA. Concentration of BYDV in barley plants showing yellow symptoms was higher in the upper to middle leaves than in the lower leaves. BYDV was frequently detected in barley and wheat plants showing yellow symptoms in the fields of Kyushu National Agricultural Eperiment Station.

View full abstract

In the soybean cultivars'Hyuuga'and 'Fukuyutaka' inoculated with soybean mosaic virus (SMV) at the seedling stage the number of grains decreased by 40% and 24%, respectively. No decrease was observed in the plants inoculated later than one week prior to flowering. The seeds, harvested from the plants that had been inoculated with SMV at the period of flowering, showed more distinct mottling than those of the plants inoculated at the seedling stage. The rate of seed transmission of 'Hyuuga'was about 10% in the plants infected with SMV from the seedling stage to one week prior to flowering. During the week preceding flowering, the later the SMV inoculation, the lower the rate of seed transmission. No seed transmission was observed in the plants inoculated after flowering.

View full abstract

A new type of lodging has been observed in some corn fields in Miyakonojo, Miyazaki, for the past 4 or 5 years. This lodging occurred when the wind was strong or relatively weak. In 1987, it was confirmed that the lodging was caused by R hizoctonia solani AG 2-2. The pathogen invaded and damaged roots. Lodging was attributed to root disease and wind velocity. In the case of lodging occur-ring when the wind was not strong, the root part of a corn plant more than 2 meter high was only a fist size. However, the corn plants was able to survive. Disease- resistance tests revealed that the 11 varieties tested were all susceptible. Furthermore, each variety of sweet corn and sorghum tested was also susceptible. The name of Rhizoctonia root rot was proposed for this new disease of corn.

View full abstract

Young seedlings of cucumber (cotyledon stage) and Nicotiana glutinosa(5-6 and 8-10 leaf stage) were inoculated with TSWV by the conventional leaf rubbing method. The inoculated plants were transferred into each of four incubators at 32, 26, 20 and 16 C. The number of diseased plants and number of leaves with symptoms per plant were counted until 20 days after the inoculation.
At a higher temperature, the test plants developed symptoms rapidly and a high degree of disease incidence. Cucumber exhibited severe symptoms and stunted growth at 32 C while no symptoms were observed at 16 C. N. glutinosa (5-6 leaf stage) inoculated with the virus and kept at 32 C showed severe symptoms and the yellowish color developed under the leaves expanded to the whole plant which eventually died. Leaf symptoms were slight at 16 C. N. glutinosa(8-10 leaf stage) showed the same symptoms, but the plant did not die at 32 C and symptoms on leaves did not appear at 16 C.
To study the effect of changes in the temperature on the symptom expression in N. glutinosa, the inoculated plants were shifted from incubators at higher (32 C) to incubators at lower temperatures (20 C) and from incubators at lower to incubators at higher temperatures at 1, 2 and 4 days after the inoculation. The plants maintained at a higher temperature continously expressed symptoms followed by the plants which remained for a longer period and were shifted early to incubators at high temperature.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The damping-off of kiwifruit occurs from the latter half of the rainy season to early summer. The trees develop satisfactorily from the time of sprouting to the elongation of new twigs, but suddenly the leaves wilt and the whole tree dies. In almost all these trees, root-rot occurred and the epidermis of crown roots was easily peeled off. In Kumamoto Prefecture, outbreaks have been recorded since 1982, and found in many orchards located in areas which were formerly used as paddy fields and in humid valleys. Although usually the percentage of the affected trees did not exceed 10%, in many areas 30% of the trees were affected by the outbreaks. As a result the destruction of the trees was associated with an economic loss. To analyze the factors involved in the outbreaks, experiments on water tolerance of potted plants of the Hayward variety were carried out. The results showed that almost all the seedlings were healthy when 1/3 of one-foot pot was flooded while 100% of the seedlings died when the whole pot was flooded. After 5 to 7 days of treatment, wilting of the leaves started and after 13 to 15 days the leaves became brown and defoliation was observed. The symptoms of the withered seedlings were nearly the same as those observed in outbreaks of damping-off in the field.

View full abstract

Growth and wing polymorphism among the immigrant populations of the brown planthopper, Nilaparvata lugens STÅL, were compared under uniform laboratory rearing temperatures. Variations in the total effective temperature and the ratio of macropterous forms were observed during the nymphal growth and in female adults. Comparison of the locations of low level jet and the collection sites of the immigrant plant hoppers, suggested that they were derived from different migration sources.

View full abstract

To analyse the seasonal prevalence of occurrence, adults of L. oryzophilus were caught in a light trap from 1985 to 1987 in Kagoshima Prefecture. At the same time, the emergence period of the first generation adults was surveyed. The emergence of the first generation adults started from June 15-20 and lasted until July 21-27, and the period corresponding to 50% emergence was July 3-10. The total emergence period was 30-39 days. There were no clear differences in the emergence period between localities and years. The mean number of adults emerged per crop ranged from 7.8 to 18.7.
There were two peaks in the number of catches in the light trap. The first peak was related to the overwintered adults in April to May. It occurred from late April to early May in 1985 and 1986, and from mid to late May in 1987. The total numbers of catches were not different from year to year. The second peak was related to the first generation adults and appeared in early July in 1985 and 1986. The total number of catches in 1985 was not different from that in 1986. The second peak in 1987 was no as clear, and adults were caught continuously until the end of August though the total number of catches was distinctly lower than in 1985 and 1986.

View full abstract

The seasonal prevalence of two stink bugs, Riptortus clavatus THUNBERG and Piezodorus hybneri GMELIN, was investigated on autumn soybean. Both insects immigrated to the fields about the middle of the flowering stage and their number increased after the grain development stage. They obviously reproduced on autumn soybean.

View full abstract

[in Japanese]

View full abstract

Volcanic ash soil infested with M. incognita was treated with "Vydate" (1% oxamyl) at doses of 300 or 400kg/ha, or with "Mocap"(5% ethoprophos)at 200 or 300kg/ha and potted for the cultivation of tomato plants at 17, 22, 27. and 32°C for 40 days in Experiment 1, and for 27 days in Experiment 2.
"Vydate", applied at the concentration of 200-400 kg/ha, significantly reduced the number of nematodes and of root-galls in the tomato root-systems at lower temperatures (17 and 22°C). However the numbers increased considerably at higher temperatures (27 and 321°C). This chemical induced the suppression of root penetration by the nematodes up to 29 days with little nematicidal action at a dosage level of 400 kg/ha regardless of the temperature. "Mocap", applied at 200 kg/ha, markedly reduced the numbers of the nematodes and of root-galls in tomato roots due to both a nematicidal effect on the nematodes in soil and inhibition of their penetration. However the numbers gradually increased as the temperature rose from 17 to 32°C.

View full abstract

Field tests were conducted to evaluate the effect of a predacious anthocorid, Orius sp. on populations of pests on eggplant using the insecticidal check method in 1987. The population of Orius sp. in the treated plot was lower than that in the untreated plot. The population of Thrips pakni KARNY and Tetranychus kanzawai KISHIDA was higher in the treated plot. These results suggest that Orius sp. is effective in reducing the population of these pests on eggplant.

View full abstract

Pupae of the diamondback moth were exposed to the ichneumonid, Diadromus subtilicornus, in test tubes at 25°C, 14L-10D. The exposed hosts were reared under the same conditions to determine the number and the sex of the wasp′s progenies. The mean number of progenies per female was 85 and the sex ratio (proportion of the females) was 0.425. The mean longevity of the mother wasps was 40 days. The net reproduction rate (R0), the mean length of a generation (T) and the intrinsic rate of natural increase (r) were estimated to be 34.85, 31.18 days and 0.118/female/day respectively.

View full abstract

A paedogenetic gall midge, Mycophila sp., which feeds on the mycelium of, the oyster mushroom, Pleurotus ostreatus, was observed in 1984 in a factory in Miyazaki Prefecture. This species was completely eradicated from the factory by the application of an insecticide. Some of the larvae were transferred to the laboratory before the application and have been reared for successive generations in order to study their ecological and physiological characteristics. By using these materials, several experiments were carried out in July 1987 and January 1988 to obtain information about the phototaxis and movement of the species. Adults in a darkened test-tube covered with aluminiumfoilwere strongly attracted to the light coming through a small window opened around the centre of the test-tube. In contrast to the adults, the paedogenetic mother larvae which were put on a sheet of moistened white paper did not exhibit a distinct positive phototaxis under unidirectional lighting. They neither moved in any particular direction under uniform lighting, nor did they show any difference in the level of activity between dark and light places. The average moving distance of the larvae was about 11mm per minute.

View full abstract

The infectivity of the nematodes Steinernema feltiae (DD-136), S. bibionis and S. glaseri to the last instar larvae of G. mellonella and S. litura was higher in this order of nematodes. As the body size of the S. litura larva increased, the three species of nematodes required a longer time to kill the host. However, such tendency was not observed in the Ga mellonella larva which was highly susceptible to the three species of nematodes. Based on the fresh weight of the host insect, the number of S. feltiae and S. glaseri nematodes which were recovered 14 days after the inoculation of ca. 1, 000 infective juveniles from G. mellonella larvae was 2.5 or 3.1 times larger than that from S. litura ones, respectively. Similarly, the number of S. feltiae, and S. glaseri nematodes recovered from G. mellonella larvae was large and 7.7 and 9.2 times as large as that from S. litura larvae, respectively. The highest infectivity and propagation of Se feltiae on S. litura larvae were observed at temperatures ranging from 24 to 27°C. At temperatures higher or lower than this range, the insect cadavers were readily colonized by fungi, mainly Aspergillus oryzae, and produced fewer nematodes. The propagation and establishment of the nematodes appear to be difficult in moist soil containing a large number of fungi and other saprophytic microorganisms.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Thirteen hymenopterous parasitoids have been obtained from the larvae and pupae of the citrus leafminer, Phyllocnistis citrella collected from several districts of Kyusyu, and Wakayama prefecture in Honsyu, Japan. They consited of one Braconid, 11 Europhids and one Elasmid. Both Sympiesis striatipes (Eulophinae) and Tetrastichus sp. (Tetrastichinae) were the dominant species in most of the districts. In some cases, Visnuella sp. (Entedontinae) or Chrysocharis sp. (Entedontinae) was also relatively abundant. The surveys conducted from late July to late October in 1987 at Kuchinotsu showed that the mortality reached maximum values during the 3 rd instar larval stage. Total mortality and parasitism in this stage ranged from 61 to 78%, and 17 to 31% respectively.

View full abstract