During a survey for plant-parasitic nematodes of commercial ornamental plant nurseries in Japan, four populations of Xiphinema brevicolle Lordello et Costa, 1961 were detected from root zone soil samples of Japanese holly (Ilex crenata Thunb. ) at four locations and examined to study the intra-specific variations. Two populations are comparatively larger in body size than the other two though their morphometrics overlap. Phylogenetic analysis of DNA sequences of the mitochondrial COI region by Maximum Likelihood method revealed two divergent groups among the six sequence variants whereas DNA sequences of the nuclear 18S rDNA region and the nuclear large subunit rDNA D2/D3 region were of little use to clarify the relationship between the populations. Referring to the two COI groups, differences within each group (< 0.5%) are regarded as intra-populational variations and those between the two groups (7.2-7.6%) are regarded as inter-populational variations. One population only accommodates individuals of both of the COI groups and has a wider range of body lengths than the other populations. Finally, this population is considered as a collection of conspecific but clearly distinct populations and such a case may be a burden in examination of a given sample of X. americanum-group species because a cohabitant mixture of distinct conspecific populations with visually undetectable differences may be present.

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The pinewood nematode (PWN), Bursaphelenchus xylophilus, was cultured on the gray mold fungus, Botrytis cinerea, grown on potato-dextrose-agar medium (Pearlcore PDA‘Eiken') diluted 5 times and supplemented with glycerol (3%) in a flattened culture bottle (area of the base: 24 cm²). The mean number of dispersal 3rd stage juveniles (DSJ₃) and the mean percentage of DSJ₃ in the populations of PWN were 31,688 and 20.8% at 30 days culture. The numbers of nematodes and DSJ3 on PDA supplemented with glycerol obviously peaked higher and later than non-supplemented PDA. Dispersal 4th stage juveniles (DSJ₄) developed in the culture bottles when B. xylophilus nematodes were co-incubated with pupal and adult Monochamus alternatus on the fungus. DSJ₄ (mean number, 17,446) were collected from 8-day-old M. alternatus adults that had been co-incubated with B. xylophilus during pupal and adult stages. This medium supplemented with glycerol is useful for stabilizing nematode incubation and obtaining DSJ₃. In addition, this method is useful to clarify the mechanism of DSJ₄ induction.

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To use steinernematid entomopathogenic nematodes as a biological control agent against the ambrosia beetle, Platypus quercivorus, the vector of Japanese oak wilt, their host-finding behavior, insecticidal activity and penetration capability were examined using a tiny glass tube system (simulated gallery system; SGS). In the SGS, Steinernema carpocapsae more vigorously moved to P. quercivorus larvae than to Galleria mellonella larvae, a well-known suitable host. Also S. carpocapsae showed high insecticidal activity against the larvae and adults of P. quercivorus by the inoculation assay, while insecticidal activity of S. glaseri against the larvae of P. quercivorus was low. In the case of S. carpocapsae, the number of nematodes invading the larvae or adults of P. quercivorus increased with an increase in the number of nematodes applied, and thereby insecticidal activity also increased. This suggests high potentialities of S. carpocapsae in its infection and insecticidal activity against both larval and adult stages of P. quercivorus, while S. glaseri showed no positive infectivity against the larvae of P. quercivorus. However, S. carpocapsae was little attracted to the extracts (ethyl ether/ethanol) of P. quercivorus larvae and adults, although strongly attracted to those of G. mellonella larvae. On the contrary, the movement of S. glaseri was enhanced by the extracts of P. quercivorus larvae and adults, but not by those of G. mellonella larvae.

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