Root knot nematodes(Meloidogynespp) are a serious problem of vegetable production in Tanzania and feasible control methods are lacking. In this study, marigold plants(Tagetes minutaandT. erectawere compared to nematicides ethylene dibromide and aldicarb for control of root knot nematodes. Of the three, ethylene dibromide gave the most effective reduction of root galling and the poorest shoot growth and fruit yields, aldicarb gave the highest shoot growth and fruit yields and reduced the number of root galls by a factor of 21 in glasshouse conditions.Tagetes erectaand T.minutareduced the number of galls by a factor of 4 and 6 respectively over the non‐treated controls. Similar results were observed in field conditions. There was a negative correlation between the reduction in number of root galls and the Increase in plant growth or fruit yields in treatments with aldicarb and marigold plants, but not in treatments with ethylene dibromide. This indicated phytotoxic effects of ethylene dibromide.