The effect of culture filtrates (CF) of Aspergillus flavus, A. fumigatus, A. ochraceus, Penicillium isolandicum, P. notatum, and P. urticae on root-knot nematode, Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis, was studied. CF of all the tested fungi were responsible for considerable reduction in root and soil populations, maturation and reproduction of both nematodes. These CF were considered to be lethal to the nematodes, and/or affected movement and penetration of host roots. All CF tested improved growth of the host plant. Jpn. J. Nematol. 20: 1-7 (1990).

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Population changes in both eggs and juveniles (J2) of Meloidogyne incognita were studied in a sweet potato field from autumn to the following spring. Field populations of the two nematode stages were estimated by a combination of a sieving-decanting technique and a bioassay. In October and November the majority of M. incognita in the field were J2. At least 30% of the total population in autumn survived until late May. In another experiment egg-masses of the nematode, detached from or attached to roots of sweet potato, or newly hatched J2 were stored in the field in autumn. When stored by the middle of October, most of the eggs, irrespective of the types of egg-masses, hatched until December when soil temperature decreased below 10°C. At least 60% and 27% of the J2 hatched from detached egg-masses stored in September and October, respectively survived until May. Many eggs in egg-masses stored in November remained unhatched in December, but the majority of these eggs did not hatch the following spring. Overwinter survival of freshly hatched J2 stored in autumn varied with time of storage. Survival was lowest in those J2 stored in September due to decline of their populations until December. The results suggest that in Kyushu J2 are the predominant overwintering form in fields of sweet potato and other crops grown under similar conditions to this study.

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The number of Bursaphelenchus xylophilus (PWN) carried by Japanese pine sawyer beetle, Monochamus alternatus, was examined in its relation to the density of PWN in the logs of Pinus thunbergii and P. koraiensis, blue stain in the wood, and abundance of ascocarps of Ceratocystis spp. on the wall of pupal chambers of M. alternatus. A significant positive relationship between degree of blue stain and the density of PWN was found in the wood of P. koraiensis logs, whose blue-stain degree was lower and more variable than that of P. thunbergii logs. The degree of blue stain was also significantly related to water content of wood and abundance of ascocarps of Ceratocystis spp. growing over the pupal chamber walls. Pine sawyer beetles emerged from P. koraiensis logs carried significantly fewer number of PWN than those from P. thunbergii logs. Especially, beetles from P. koraiensis logs whose water content was lower than 30% carried no PWN or less than 200 PWNs. There was no significant relationship between the density of PWN in wood, the density of PWN remaining around pupal chambers and the number of PWN carried by M. alternatus. Jpn. J. Nematol. 20 18-24 (1990).

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Bursaphelenchus xylophilus and its closely related species, B. mucronatus were successfully propagated well on calli of tobacco (Nicotiana tabacum), alfalfa (Medicago sativa) and several pine species. Different propagation rates or different maximum populations were recorded. Most nematodes occurred in the outer layer of the callus, in which cells appeared to be dead. Tannin accumulated in the nematodeinoculated callus tissues. The correlation of the tannin content with the number of nematodes was also examined. Jpn. J. Nematol. 20: 25-36 (1990).

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Tomato (Lycopersicon esculentum) seedlings with five leaves planted in clay pots (20cm diam.) containing two l of andosol, sirasu soil, sand-dune regosol or gray lowland soil, respectively, were inoculated with Meloidogyne incognita second stage juveniles at six inoculum levels (0 to 33, 000 per pot) and cultured outdoors for 40 days. Plant heights which ranged from 77 to 89 cm at inoculum 0, were reduced by 6 to 10 cm at inoculum 33, 000 in each soil except for gray lowland soil. Average top weights (shoots+fruits) were 284, 157, 127, and 122g for sirasu, gray lowland, andosol, and sand-dune regosol, respectively. Root weights increased with increasing inoculum levels in each soil. Percentage of roots to total plant weights (shoots+fruits+roots) were smaller in sirasu (20% on the average) than in other soils (25 to 27%). A stimulatory effect on the plant growth was observed at low inoculum levels in andosol and sand-dune regosol. Chemical properties of soils tested did not show any association with differences in plant growth affected by nematode infection.

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Plant-parasitic nematodes of mainly vegetables, field crops and fruit trees were surveyed in Uruguay. Meloidogyne spp. of tomato and potato, Ditylenchus dipsaci on onion, and Pratylenchus vulnus on strawberry caused serious injuries to these crops. P. scribneri, the first record from South America, was common in natural grasslands and sugarcane fields. Jpn. J. Nematol. 20: 44-50 (1990).

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