Factors affecting the infection of alfalfa seedlings by Ditylenchus dipsaci.

Experiments were conducted to determine the effects of plant confinement, soil type, watering practices, stage of seed germination, inoculum level, and method of applying inoculum on stem nematode (Ditylenchus dipsaci) infection of alfalfa (Medicago sativa) seedlings grown in soil. Results indicated that (i) confining seedlings together with the nematodes in small vials offered no advantage over growing plants in large flats, (ii) a very fine sandy-loam soil was superior to a fine sand for stem-nematode penetration, (iii) nematodes penetrated seedlings more readily if the soil was not watered immediately after planting and inoculation, (iv) germinating seeds with a radicle length of 0.6-1.3 cm had the highest nematode penetration, and (v) highest penetration occurred when the nematodes were placed directly upon germinating seeds. The optimum inoculum level was 50 nematodes per seedling.