Pratylenchus spp. are among the pests most frequently detected during quarantine inspections of ornamental trees. Ornamental trees are treated with nematicides to eliminate Pratylenchus before export from Japan. Three nematicides, abamectin, fosthiazate and imicyafos, have been registered for use against Pratylenchus in ornamental trees; however, their effects on Pratylenchus eggs have not been investigated. We observed the hatching rate of P. penetrans eggs after immersion in these nematicides. Benomyl, fenitrothion and fluopyram were tested for comparison. Treatment with abamectin, fosthiazate and fluopyram solution for 24 h at 25°C significantly decreased the egg hatching rate; the lowest (5.9%) in fosthiazate compared to 52.3% in the control. However, when eggs were immersed at 10°C the hatching rates of fosthiazate and fluopyram treatment groups were significantly higher than those at 25°C. Eggs treated with abamectin, fosthiazate, fenitrothion and fluopyram concentrations 10 times lower than the registered concentrations for 14 days at 10°C significantly decreased the hatching rates; however, the rate was 29.0% (fluopyram) or more compared to 49.2% in the control. These results suggest that the nematicide effect on eggs may be limited under winter treatment conditions commonly used for ornamental trees.

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Stunt nematodes detected in three fields of komatsuna (Japanese mustard spinach) in Tokyo were identified as Tylenchorhynchus zeae based on morphological observations, sequences of D2/ D3 fragments of the 28S rRNA gene, the internal transcribed spacer region of rDNA and partial 18S rRNA gene. The PCR-RFLP analysis of the 48 samples showed the same digestion pattern and did not indicate the occurrence of multiple species. The pathogenicity of this nematode to komatsuna remains to be elucidated.

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