Biological indices generated using the CARD (curve-fitting allelochemical response data) model may be useful in crop-bio-nematicide interactions since they provide information related to the stimulation dosage of the material to the crops. The objective of this study was to determine: (1) Whether selected crops in the Gramineae family respond to crude extracts of Cucumis myriocarpus fruit in density-dependent patterns, and (2) the appropriate dosage of crude extracts of C. myriocarpus fruit when used as a pre-plant bio-nematicide in Gramineae family. Separate studies using three maize, millet and sorghum were conducted under greenhouse conditions with ten treatments (0, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00 and 2.25 g material/pot), arranged in randomised complete block design, with five replicates. At harvest, 18 days after treatment, the CARD model demonstrated that the responses of plant organs when regressed on a series of crude extracts of C. myriocarpus fruit stimulate exhibited the density-dependent growth patterns, with various organs having different sensitivities to the material. The integrated sensitivity of the measured variables showed that the test crops differed with increasing order of sensitivity to the test material with increasing order of sensitivity to the material being sorghum > maize > millet. Estimated mean dosage response for stimulation (MDRS) for maize, millet and sorghum being 1.13, 0.86 and 1.12 g, respectively. In conclusion, at low dosages crude extracts of C. myriocarpus fruit stimulate plant growth and, therefore, have the potential for use as pre-emergent bio-nematicide in maize, millet and sorghum production.
Key words: Biological indices, CARD model, density-dependent growth patterns, maize, millet, sorghum.
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