Plant parasitic nematode populations as influenced by onion based cropping sequences

The population dynamics of seven plant parasitic nematodes viz., Rotylenchulus reniformis, Helicotylenchus dihystera, Hoplolaimus seinhorsti, Pratylenchus delattrei, Meloidogyne incognita, Xiphinema basiri and Tylenchorhynchus sanwali, was studied in onion-based cropping sequences. In onion – maize - onion cropping sequence, the populations of R. reniformis and P. delattrei were increased whereas in onion – tomato - okra cropping sequence, the populations of H. dihystera, H. seinhorsti and M. incognita were increased but in both the cropping sequences the populations of T. sanwali and X. basiri were maintained without major fluctuations. The populations of all the seven species decreased during fallow period in both the cropping sequences. Relative humidity had no profound influence on nematode populations.