Investigations on the effects of some different plant materials in control of Root-knot nematodes [Meloidogyne incognita (Kofoid & White) Chitwood] This study was conducted during 2006-2007 as pot experiment in order to investigate the possibilities of some alternative methods against root-knot nematodes in the climatized room and greenhouses at Plant Protection Department, Agricultural Faculty, Ege University. The main material of experiment consisted of root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] infected tomato roots and soils, “Rio Grande” cv tomato plants, the leaves of castor oil plant [Ricinus communis L. (Euphorbiaceae)] and oleander [Nerium oleander L. (Apocynaceae)], the fruits of squirting cucumber [Ecbalium elaterium L. (Cucurbitaceae)] and whole plants of American marigold [Tagetes erecta L (Asteraceae)]. According to the findings obtained this experiment, it was determined that the all plant material treatments have less gall index value and placed statistically (P≤0,05) in different group compared with positive control. The least gall index value was determined in the characters in which the leaves of castor oil plant amended the soil (2,8 ± 0,20), placing in the same group with the control plants used with nematicides (3,0 ± 0,39) and evaluated as the most effective treatment. Besides this, in the evaluation done at the end of this experiment in terms of the numbers of second stage juvenile of root-knot nematodes, there were no nematode juveniles in the soil of castor oil plant characters. In the other plant treatments, there were less numbers of second stage juvenile of root-knot nematodes and placed statistically (P ≤ 0,05) in different group compared with positive control treatments. In terms of plant growth characters such as plant height, compound leaves, root growth scale and fresh root weight, it was evaluated that the tomato plants in the all plant treatments have got the better growth than the positive control tomato plants