The present invention relates generically to compositions used for controlling agricultural pests and, in a particular embodiment, to compositions usable for combating nematodes.The invention presents a feasible alternative to the use of nematotoxic compounds that are harmful to the environment and that may damage human health. This alternative is embodied through a nematotoxic composition for controlling nematodes and that may be used on plants, parts of plants and on the soil. The respective technology results from unexpected results achieved from experiments carried out with extracts of the plant Canavalia ensiformis, resulting in an unheard-of nematotoxic composition comprising a specific combination of substances that are naturally found in the extract and that act synergistically.