The nematicidal activity of common buckwheat (Fagopyrum esculentum Moench) on the root knot nematode Meloidogyne incognita race 1 was evaluated using serial dilutions. The methanolic extract of the dried plant presented an anthelmintic activity with an EC50=62.6 ± 26 and 40.8 ± 26 µg/ml after 48 and 72 h of immersion respectively. However, the extract from fresh plant was less active with EC50=127.7 ± 67 and 98.3 ± 54 µg/ml after the same period of immersion. Nematicidal activity of the most abundant aldehyde (salicylaldehyde) and other aldehydes with chemical similarities were then assessed according to fosthiazate control. The most active aldehyde was salicylaldehyde (2-hydroxy benzaldehyde) followed by 3-hydroxy benzaldehyde, 4-hydroxy benzaldehyde, benzene acetaldehyde and benzaldehyde with EC50 of about 11 ± 1; 31 ± 22; 75 ± 23; 168 ± 52 and 300 ± 110 µg/ml after 1 day of immersion, respectively. As a complementary experiment, the synergistic activity was evaluated for salicylaldehyde and 3-hydroxybenzaldehyde, salicylaldehyde and 4-hydroxybenzaldehyde and for salicylaldehyde and benzenacetaldehyde. Synergistic activity was observed in the first 2 cases with EC50 after 24 h of immersion of 8 ± 2.5 and 6 ± 2.3 µg/ml, respectively. The addition of salicylaldehyde to benzenacetaldehyde enhances significantly the activity of this latter to become 23 ± 4 µg/ml after the same immersion period. The obtained results show that Fagopyrum esculentum could be considered as potent nematicidal plant to face root knot nematodes and integrated in the pest management system.