Interactions of Helicotylenchus dihystera, Pratylenchus pseudopratensis, and Tylenchorhynchus gladiolatus on two plants from the Soudano-Sahelian zone of West Africa

Interactions between Helicotylenchus dihystera, Pratylenchus pseudopratensi s, and Tylenchorhynchus gladiolatus were studied on millet (Pennicetum typh oides) and acacia (Acacia holosericea). Interactions between H. dihystera a nd P. pseudopratensis were similar on both plants; reproduction of each was lower when the other nematode species was present. T. gladiolatus reproduc tion was stimulated in the presence of the other species on millet, whereas it was inhibited on acacia at the lowest inoculum levels (50 and 200 nemat odes/plant). Damage to plants was not density dependent. Damage to millet d iffered with the species composition of the community. Only monospecific po pulations of T. gladiolatus and P. pseudopratensis significantly reduced th e miller biomass, particularly the root system. H. dihystera reduced the pa thogenicity of the two other species on this plant. Each nematode assemblag e suppressed dry shoot and root weight of acacia; most assemblages reduced rile number of Rhizobium nodules on the root system.