Intensity of nematode infestation in mandarin orange crop in nilgiris hill region

Six genera of plant parasitic nematodes viz., Tylenchulus semipenetrans, Helicotylenchus spp., Rotylenchulus reniformis, Xiphinema basiri, Hemicriconemoides sp. and Pratylenchus coffeae were found associated with mandarin orange in Nilgiris district. Among them the citrus nematode T. semipenetrans was the predominant nematode pest with absolute frequency and relative frequency of 90.52 and 37.07 per cent respectively in soil and 75.78 and 33.02 per cent respectively in root. Among the seven villages surveyed Kengarai and Kolagiri villages in Kotagiri taluk recorded severe infestation. High degree of decline and dieback symptoms were observed in the infested areas.