With the aim of determining the nematicidal effect over Meloidogyne incognita in beans, (variety “Centa Cuzcatleco”), we evaluated the watery extracts of garlic (Allium sativum), marygold (Tagetes sp), papaya tree (Carica papaya tree), and “barrenillo” grass (Cynodon dactylon), during the period of 1993-1994. Tests were conducted at the laboratory and the greenhouse, with the use of a completely random design, with six treatments and eight repetitions. The research was conducted at the Center of Agricultural and Forestry Technology (CENTA): In the greenhouse the seedlings were inoculated with 4.000 eggs and J2 of M. incognita, and then treated with the aforementioned plant extracts. In addition, we used the nematicide Phenamiphos and an absolute check (plain water) in the laboratory, the juvenile stages of the nematodes were exposed to direct contact with each one of the substances, and afterwards they were rinsed in water to measure its recuperation. Sixty days after sowing, we measured the variables: final height, fresh and dry weight of foliage, fresh weight of roots, final nematode population, gall index, and reproduction rate. The best extract for controlling M. incognita at the greenhouse was papaya tree (smallest gall index), even though Phenamiphos was the overall best treatment. The extracts of garlic and papaya tree, in dosis of 35 g per plant , provoked toxicity in the plant. At the laboratory, the extracts which produced a higher mortality rate of juvenile nematodes were garlic, marygold and papaya tree. The fastest mortality