Filenchus japonicus n. sp. collected from rhizosphere of Scirpus wichurai forma concolor in Mt. Aso, Kumamoto has two incisures of lateral field, large spear knobs, functional spermatheca, and tail nearly as long as vulva-anus distance. On these bases, Tylenchus filiformis: DAS, 1960, nec BÜTSCHLI, 1873 was synonymized with the new species, although it differed from the latter in larger MB value (50 vs. 43), more rounded median oesophageal bulb, shorter body, etc. From T. filiformis: THORNE, 1961 nec BÜTSCHLI, 1873, this new species was distinguished by the longer body, tail nearly as long as vulva-anus distance, two incisures of lateral field, and presence of functional spermatheca. It differed from T. vulgaris by having large spear knobs, lateral field with two incisures, and wider annule at mid-body (1.5μm vs. 1.0μm). Tylenchus vulgaris and T. exiguus were considered distinct species and were trasf erred to Filenchus. Ottolenchus helenae from rhizosphere of Cirsium suffultum in Mt. Aso, Kumamoto was a new record of the species from Japan and was redescribed. Jpn. J. Nematol. 16: 1-9 (1986).

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The in vitro culture experiment was conducted to study the effct of linoleic and oleic acids, the major unsaturated fatty acids in the pine cell resin, on the growth of the pine wood nematode, Bursaphelenchus xylophilus. The media used were the basal medium consisted of 3% soytone and 2% yeast extract and those supplemented with linoleic and/or oleic acids at the concentration of 0.1% and 0.01%. To 5 ml of these media in a test tube, inoculation was made aseptically witha water suspension of nematodes in which the 4th stage larvae (L₄) predominated. Nematodes in the supplemented media showed dark body color resulting from densely packed lipid droplets in the intestine. Both linoleic and oleic acids stimulated the molting of L₄ to adults. Adults in supplemented media produced man more eggs and resulting L₂ than those in unsupplemented media. The maturation of progeny to produce the following generation did not occur in any culture media tested. Nematode population was maintained for more than 90 days in all tested media. Those nematodes kept their ability to reproduce on Botrytis cinerea and they also maintained the ability to induce wilting of seedlings. Jpn. J. Nematol. 16: 10-20 (1986).

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Histochemical investigations on the localization of acetylcholinesterase (AChE) in the body of Bursaphelenchus xylophilus were carried out. Monoxenically cultured nematodes were washed with water, fixed with 4 % formaldehyde potassium phosphate buffer, sonicated for 30 secs. to enhance the permeability of the staining mixtures through the cuticle, and stained for the determination of the AChE activity with acetylthiocholine as a substrate by the method of KARNOVSKY & ROOTS' which allows a fine and precise localization of the decomposed substrate. The region intensely stained was located between the metacorpus and the intestine where a nerve ring and associated ganglia are present in nematodes. The areas which were weakly stained consisted of the dorsal and ventral nerves, the circumference nerves of the reproductive organs, amphidial nerves which include cholinergic nerves. The variations in the degree of staining among the dipping solutions indicated that most part of the cholinesterases present mainly in the central nervous system of B. xylophilus consists of the specific cholinesterase. The paralysis caused by methomyl seems to be associated with the inhibition of AChE in the cholinergic nerve of this nematode.

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The entomogenous nematode, Steinernema feltiae (Mexican), were evaluated both in the laboratory and in the field for their use for the control of 3rd instar larvae of the fall webworm. The larvae were infected and then killed by S. feltiae within 24 hrs at the rate of 1, 000 and 5, 000 infective juveniles (J_m) per insect larva and killed within 48 hrs at the rate of 100 and 500 J_m per larva at 25°C under laboratory conditions. In the first trial (June 24-26, '85), when the humidity was very high and the temperature moderate, the nematodes persisted on the leaf surface of cherry trees even 40 hrs after application. The infestation of nematodes at the rate of 3, 000 J_m/ml resulted in 100% mortality of the fall webworm 17 hrs after foliage application. In the second field trial (June 27-29, '85), under high humidity and low temperature conditions, a higher survival rate of the nematodes and a higher mortality rate of the insect were obtained for higher concentrations of the nematode water suspension. In the third field trial (August 15-16, '85) when the humidity and temperature conditions were favorable for the nematode persistence 11 hrs after application, and thereafter became unfavorable in the daytime, nematodes sprayed on the surface of the leaves died 22 hrs after the application. The mortality of the insect larvae, however, reached 85.1% at the rate of 3, 000 J_m/ml.This concluded that _{S. feltiae} (Mexican) can be use as biological control agents against the fall webworm on tree leaves.

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The resistance of two susceptible and six resistant soybean varieties to Heterodera glycines (SCN) was determined for six soil temperatures from 12 to 35°Cby comparing the number of cysts which multiplied with those of the susceptible variety “Lee 68” after completion of two generations at each temperature. In three populations of SCN grown on susceptible varieties the optimum temperature for nematode development ranged from 20 to 25°C, and temperatures of 12°C and 35°C were unfavourable. In two resistant varieties of the “Gedenshirazu” group the level of resistance decreased along with the rise of the temperature and became comparable to that of the susceptible variety at 25°C. The effect of temperature on the resistance was least appreciable in the “Peking” group varieties.

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Silica gel column chromatography, reverse phase column chromatography and silica gel thin-layer chromatography were employed for isolating the dauer juvenile (DJ) inducer from the methanol extract of Caenorhabditis elegans and also of staled axenic culture medium. The bioassay of the inducer was carried out by determining the DJ recovery inhibition activity using 1/8 strength liquid axenic culture medium. Although, the DJ inducer was not purified, it was found to be soluble in methanol and did not show ninhydrin reaction. On the thin-layer chromatography, only in the solvent system consisting of chloroform-methanol-acetic acid (60: 40: 1, v/v), a single active spot with slight UV quenching was observed at Rf 0.8.

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In November, 1984, the occurrence of a species of the genus Ditylenchus was found in diseased garlic plants which were collected in a field of Kizukuri-machi, Aomori Prefecture. The nematode species was identified as the potato-rot nematode, Ditylenchus destructor THORNE. Although this nematode had been known to attack several plants, garlic had not been reported hitherto as a host of the nematode. From 1984 to 1986, a nematode survey was conducted in garlic fields in Aomori Prefecture and it was recognized that the total area of the infested garlic fields had extended over about four hectares. When the nematode-infected bulbs were planted, many garlic plants died in the early stages of the growth period, and/or the basal plates of garlic bulbs in most of the plants which survived became dark and rotten at harvest time.

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The development of the inoculated second stage larvae of Meloidogyne incognita and the histological changes in the roots of three enemy plants, Arachis hypogaea, Crotalaria spectabilis and Macroptilium atropurpureum and in those of a host plant, Lycopersicon esculentum were observed. Large root-knots were observed in L. esculentum as early as 5 days after exposure to the second stage larvae and moderately enlarged ones were induced in Mac. atropurpureum and C. spectabilis after 6 and 10 days, respectively, while no visible changes appeared in the roots of A. hypogaea. In the L. esculentum roots, giant cells started to develop 5 days after inoculation and became well developed after 14 days, showing many enlarged nuclei, a dense cytoplasm and thickened cell walls and after 24 days mature females with egg-masses appeared. In both Mac. atropurpureum and C. spectabilis, giant cells were similarly induced, but in the former plant the cytoplasm was vacuolated and the thickening of the cell wall was moderate even 13 days after inoculation, while two thirds of these cells degenerated up to 23 days after inoculation. In the roots of that plant only a few larvae were sexually differentiated and none of them developed beyond the second stage and eventually some degenerated untill 33 days after inoculation. In the latter plant the infecting larvae showed small genital primordia and remained sexually undifferentiated in spite of the formation of developed giant cells which persisted until 35 days. Necrosis was sometimes observed as well. In the A. hypogaea roots, most of the larvae were observed outside of the central cylinders within 2 mm from the root tips and they did not develop at all. Necrotic and empty cells were always observed in contact with those larvae and along the tracks of penetration.

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Changes in the populations of Meloidogyne incognita (second stage larvae), Helicotylenchus spp.(H. dihystera predominant), and free-living nematodes (including Aphelenchus avenae, Rhabditis, and more than six unidentified genera) at various depths of the soil profile in a sweet potato (Ipomoea batatas LAM.) field were investigated during the period of seven weeks after the setting of plant vines. The number of M. incognita per 10-ml soil in the rhizosphere within the rows (22 cm high) which was about 20 until four weeks after plant setting rapidly decreased to 3 in the fifth week, followed by a steep rise to about 100 in the seventh week due to the presence of newly hatched larvae. In contrast, 23 to 40 larvae were observed immediately below the rhizosphere within row (basal portion of the row), and as many as 80 individuals at depths ranging from 5 to 30 cm from the furrow surface. A gradual decline in number was apparent in these deeper habitats. The number of larvae in the surface layer of a row (till 3 cm depth) also fluctuated as in the rhizosphere within rows. Helicotylenchus spp. inhabited all the depths examined (from the surface of the row to 30 cm deep under the furrow surface) in the third week and they were more abundant in the rhizosphere within rows as well as the surface layer than in the deeper habitats in the fourth and seventh weeks. Free living nematodes, which were commonly scattered at various depths in the third week, disappeared in deeper areas with time. The populations of M. incognita in the rhizosphere within rows and in the deeper habitats appear to be ecologically different from each other and/or rather independent.

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The pine wood nematode, Bursaphelenchus xylophilus, was found to reproduce on callus tissues of Pinus densiflora and P. thunbergii which are susceptible to pine wilt caused by this nematode and on callus tissues of lucern and cryptomeria which are not the hosts of this nematode. In the inoculation test in the United States, P. jeffreyi showed low susceptibility. The objectives of the present study were to determine the propagation of the nematode on callus tissues of P. jeffreyi compared with those of P. densiflora and P. thunbergii and to examine the difference between callus tissues and ordinary seedlings of P. jeffreyi in the propagation of this nematode.

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