The present application relates generically to compositions used for controlling agricultural pests and, in a particular, to compositions usable for combating nematodes. The application presents a feasible alternative to the use of nematotoxic compounds that are harmful to the environment and that may damage human health. This alternative includes a nematotoxic composition for controlling nematodes 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.