Behaviour of the systemic nematicide oxamyl in plants in relation to control of invasion and development of Meloidogyne incognita

SUMMARY A single foliar application of oxamyl (12.5 μg) in acetone significantly reduced invasion of cucumber seedlings by Meloidogyne incognita juveniles for at least 21 days but did not affect the early stages of development of juveniles which had already invaded the roots. In contrast, application of oxamyl to the roots significantly reduced both invasion and development of juveniles. Concurrent studies using radiolabelled oxamyl showed that the amount of toxicant in the roots after 3 days was 13 times greater following root application than after foliar treatment. It is probable that oxamyl concentrates at the sites of nematode attack as an overall concentration of only 3 ng oxamyl g‐1 root was sufficient to prevent invasion. Much greater concentrations than this were required to affect the nematode in vitro. Oxamyl appeared to be lost from the roots into the soil principally in the form of its non‐toxic oxime and it is suggested that the site of action following foliar application is at the root surface or outer cortex. Studies on the invasion behaviour of M. incognita juveniles on agar showed that the action of oxamyl had a sensory component.