Abstract

                                Root-knot nematodes (Meloidogyne spp.) have become a serious problem in many vegetable growing tracts of our country. The ubiquity of such nematodes in poor soils particularly those devoid of organic matter is perhaps mainly responsible for the extensive infestation consequently leading to low yield and poor quality of a number of vegetable crops. Unbalanced application of fertilizers not only leads to severe repercussion on plant itself but in many cases it increases the reproductive rates of nematodes (Oteifa and Khalil, 1961). The deficiency of phosphorus and potash in some Bihar soils was reported to be responsible for heavy infestation of the nematodes in tomatoes, brinjal and bhindi (Lall and Hameed, 1965). In recent years, the use of organic matter in different forms has been reported to reduce nemic population in soil (Hutchinson, 1960 and Mankau, 1963). Tho organic matter being either directly toxic to the nematode (Ellenby, 1945), or may interfere with respiration and oxidation processes in the nematode body (Renninger, et al., 1958) or alter the oxygen, nitrogen, and pH status of the soil (Mankau, 1963). Linford et al. (1938) observed reduction of soil populations of root-knot nematodes as a result of decompo- sition of organic matter in the soil which in turn supported building up of large populations of plants and animal forms destructive to nematodes including nematode capturing fungi, non-trapping fungal parasites, predaceous nematodes and predaceous mites. These collectively destroyed root-knot nematodes as well as free living forms in early weeks of decomposition. Recently, a number of soil cakes have been tested by various workers against these nematodes. Lear (1959) tested castor cake against M. javanica Treub. Singh (1963-64) reviewed the role of different organic matters used as biological control agents against different plant parasitic nematodes while reporting the efficacy of karanj (Pongamia pinnata) cake as compared to fumigants, green manuring, etc. against M. javanica. In view of this a pot experiment was conducted at Bihar Agricultural College, Sabour during winter 1964 to study the relative efficacy of different types of easily available oil cakes and the effect of their decomposition against Meloidogyne spp.

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