Peppermint (Mentha piperita L.) is one of the most economical aromatic and medicinal crops useful in pharmaceutical and agro-allied industries globally. It is among the neglected crops currently receiving attention by organic agriculture experts in Nigeria. In view of the potential threat Plant-Parasitic Nematodes (PPN) pose to the crop, a study was conducted to appraise the effects of Arati-OBD+ organic fertilizer in the control of associated phytonematodes in a field in Abeokuta. Responses of Free-Living Nematodes (FLN) to the organic fertilizer were also recorded. The fertilizer was applied at 0 tha-1, 5 tha-1 or 10 tha-1, laid out in Randomized Complete Block Design with three replications. Five core soil samples were collected randomly from the rhizosphere at depth of 0-30 cm, once every month for the period of three months per plot. Soil samples per plot were bulked to form a composite sample from which 250 g sub-samples were obtained and assayed for nematode presence, type and numbers of each found. Results indicated that 11 genera of PPN were found in the organic peppermint tested. They included Helicotylenchus, Rotylenchus, Rotylenchulus, Meloidogyne, Longidorus, Aphelenchus, Radopholus, Tylenchulus, Ditylenchus, Hoplolaimus, Pratylenchus and some free-living nematodes. These nematodes varied significantly (P 0.05) across treatments. Application of Arati-OBD+ at 5 tha-1 and 10 tha-1 significantly (P 0.05) suppressed PPN compared with untreated (control) plots. Ditylenchus, Tylenchulus, Meloidogyne, Radopholus and Aphelenchus decreased by up to 100% (total control), Helicotylenchus by 73 - 50% and Rotylenchus by 60 - 33% in the treated plots while the FLN increased by as much as 18 - 47% in the soil following application 5 – 10 tha-1
