![]() | Only 14 pages are availabe for public view |
Abstract Currently, nematologists involved in the biological control of nematodes have adopted two main strategies: the manipulation of indigenous natural enemies in soil by using organic matter, and the introduction of selected agents as inundative treatments. Some organic materials contain nematoxic chemicals and when these materials are used as soil amendments, the nematicidal principle is released into soil and is directly responsible for the suppression of nematode populations. Moreover, some microbial antagonists by themselves release toxic substances. The present investigation tackeled the problem of the biological control of root-knot nematode, Meloidogyne incognita, using introduced microbial antagonists in an alien soil environment, and incorporating plant materials of different C/N ratio in soil. The effect of these two components, viz., antagonists and plant materials, was also studied on the soil-inhabiting entomopathogenic nematode, Heterorhabditis bacterio-phora. The efficacy of five microbial agents, Bacillus circulans, B. megaterium, Serratia marcescens, Streptomyces sp., and Trichoderma viride, were tested against the second juvenile stage (J2s) of M. incognita (Mi), in the laboratory in cups, and in the screenhouse on tomato seedlings in pots, and on the third juvenile (IJ3s) stage of H. bacteriophora (Hb) in the laboratory in cups. Chopped dried vegetative parts of marigold, Tagetes erecta (C/N 39.4:1), sunn hemp, Crotalaria juncia (C/N 33.9:1), and clover, Trifolium alexandrinum (C/N 20.2:1), rice straw, Oryza sativa (C/N 54.1:1), and sawdust were (C/N 122.3:1) singly and thoroughly mixed with soil (1% w/w) as soil amendments. The experiments were conducted in the laboratory and in the screenhouse. (1) In the laboratory (1-1) Microbes in broth culture (Mm), supernatants of broth cultures free of microbes (S), and microbes in plain water (Mw) were tested against juveniles at five dilutions (52.5x106, 26.2 x106. |