Nematodes have developed a range of abilities to more effectively acquire food resources throughout their evolution. Entomopathogenic nematodes (EPNs), by using entomopathogenic bacteria, are known to efficiently utilize insect bodies as valuable food resources. Nematodes of the genus Oscheius are recognized as freeliving, and certain species display the entomopathogenic trait like EPNs. Pathogenicity of Oscheius nematodes is believed to depend on associations with entomopathogenic bacteria. However, the interrelationship between entomopathogenic bacteria and Oscheius nematodes remains insufficiently elucidated. In this study an undescribed Oscheius nematode, designated as Oscheius sp. KHA501, was isolated using a Galleria mellonella bait trap method. Oscheius sp. KHA501 exhibited a free-living behavior and was culturable with both Escherichia coli OP50 and a bacterium that was predominantly isolated from G. mellonella carcasses after infection of Oscheius sp. KHA501. The isolated bacterium, identified as Serratia marcescens bKHA501, exhibited pronounced virulence and played a pivotal role in the entomopathogenic attributions of Oscheius sp. KHA501. Furthermore, S. marcescens bKHA501 demonstrated the capability to impede the growth and propagation of the free-living soil nematode Caenorhabditis elegans. While Oscheius sp. KHA501 does not display high but moderate entomopathogenicity, its ability to harness pathogenic bacteria enhances its role as a superior scavenger. Entomopathogenic bacteria use nematodes as a vector for dissemination, suggesting the presence of a mutualistic relationship between S. marcescens bKHA501 and Oscheius KHA501.

"Potemon", a cultivar of Solanum peruvianum and closely related species to tomato, is an effective trap crop for the control of potato cyst nematodes. It has been used for official control of Globodera pallida (Gp) present in the Okhotsk region of Hokkaido, Japan, with high efficacy. However, taking a break from growing profitable crops to grow the trap crop has had a significant impact on agricultural production. Therefore, we examined the possibility of Gp control by cultivation of “Potemon” from mid-August to October after the wheat harvest, when no profitable crops are grown. The growth of “Potemon” sown mid-August was poorer than that sown mid-June. In some cases, the effect of density reduction was slightly lower because of shortened growing period caused by adverse weather conditions such as early frost. However, Gp density decreased to 28.2% of initial density on average, with a significant difference from fallow. This study showed that postwheat cultivation of “Potemon” is a promising cultivation system that can reduce the density of Gp.

A simple root box (RB) described in a previous study for screening of nematode resistant cultivars can be used to count cyst females appearing on the RB surface as an estimate of total number of Heterodera schachtii (HS) females appearing on a root system. However, only 60% of cyst females can be seen on the RB surface because other females on roots are obscured by soil. Another disadvantage is the two RB surfaces, front and back, must be examined when counting nematodes. To overcome these shortcomings, an improved sheet root box (SRB) with a nylon mesh sheet (30 µm openings) placed between the soil and the SRB surface was proposed to observe most of the females parasitizing a root system. The roots of a test plant are prevented from growing in soil by a nylon mesh sheet but grow in the space between the sheet and the SRB surface. In this study, it was confirmed that the root system of a host plant developed only on the sheet with no roots growing into soil behind the sheet, thus nematodes appeared only on one SRB surface. The number of nematodes on the SRB surface was similar to the number on the entire root system. More than 90% of the nematodes present on the entire root system were visible on the sheet surface. SRB would allow more precise and efficient quantification of HS females appearing on root systems in inoculation tests.