Nematicidal activity of the leaf powder and extracts of Myrtus communis against the root-knot nematode Meloidogyne java']javanica

Nematicidal activity of the leaf powder, leaf extracts and formulated leaf extracts of Myrtus communis, an evergreen shrub that is widely distributed in Israel and other Mediterranean countries, was evaluated using the root-knot nematode Meloidogyne javanica in in vitro and pot experiments. Leaf powder added to sand at 0.1% (w/w) reduced the number of juveniles recovered from the sand by more than 50%. Reduction in galling index and number of nematode eggs on tomato roots was also observed by incorporating the leaf powder at 0.10.4% (w/w) in the soil in pot experiments. Leaf powder extracts with methanol or ethanol showed the highest nematicidal activity among all extracts tested. Emulsifiable concentrates of leaf-paste extract at a concentration as low as 0.005% (a.i., w/w) reduced the number of juveniles recovered from treated sand and the gall index of cucumber seedlings. The extract paste at 26 g m-2 was also effective in reducing the gall index of tomato plants in field-plot experiments. The leaf powder at 0.2% and the formulated leaf-paste extract at 0.02% were also nematicidal to Tylenchulus semipenetrans and Ditylenchus dipsaci, but not to Pratylenchus penetrans or Steinernema feltiae. At least three nematicidal compounds were found in the leaf extract upon fractionation by thin-layer chromatography. The results suggest that the leaf powder and paste extract of M. communis are potential nematicides against root-knot nematodes.