Possible nematicidal effects of plant extracts of 25 species uninfected by M. hapla were observed at the 5 times dilutions in all treatments and at the 10 times dilutions in Anemarrhena asphodeloides, Acorus calamus, Achyranthes japonica, Agrimonia pilosa, Dianthus chinensis, Geum aleppicum, Houttuynia cordata, Rudbeckia bicolor, Ricinus communis, Scrophularia buergeriana, Sesamum iindicum, Sedum kamtschaticum, and Sanguisorba officinalis. The 13 species plant extracts of 5 times dilutions were evaluated for the suppression effects on reducing densities of M. hapla by treating to C. lanceolata sown and transplanted later in pots. All the plant extracts showed suppressive effects on M. hapla except for A. pilosa. The suppressive effects of A. asphodeloides, A. japonica, A. calamus, D. chinensis, R. communis, and S. buergeriana were over 80%. When the selected plants had been incorporated into the soil before C. lanceolata was sown, the numbers of root galls, egg sacs and J₂ appeared lower in the treatment of 12 plant species than ill control except for S. indicum. But the suppressive effects were lower than the effects of selected plants being cultivated simultaneously in the field. A. calamus and A. japonica exhibited over 70% suppressive effects, among the tested plants.