Herbicidal potential of selected species to overcome weed infestation in Triticum aestivum, Zea mays and Helianthus annuus.
Filter paper and soil bioassays were performed to study the allelopathic effect of aqueous extracts of Carica papaya L., Parthenium hysterophorus L., Euphorbia helioscopia L. and Rumex dentatus L. on intact and pre-germinated seeds of Rumex dentatus, Avena fatua, Helianthus annuus, Zea mays and Triticum aestivum. Experiments were designed in CRD with five replications. The parameters studied included germination percentage, radicle length (cm) and plumule length (cm) of test species. C. papaya and P. hysterophorus leaf aqueous extracts decreased the emergence of R. dentatus and A. fatua in soil bioassay while on filter paper, all extracts inhibited the germination of R. dentatus and A. fatua. In direct seeding, filter paper bioassays, radicle growth of R. dentatus and A. fatua were decreased by all the extracts. In some experiments, plumule of A. fatua was significantly repressed by E. helioscopia extract. In direct seeding soil bioassays, E. Helioscopia reduced the radicle length of R. dentatus and A. fatua. R. dentatus radicle growth was also significantly inhibited by P. hysterophorus. All aqueous extracts in soil inhibited the plumule length of R. dentatus and A. fatua. In seedling filter paper and soil bioassays, P. hysterophorus significantly inhibited radicle as well as the plumule of all test species. P. hysterophorus and E. helioscopia aqueous extracts were evaluated as good weed suppressants. Weed suppressive effects of these extracts can be attributed to allelopathic secondary metabolites that are further needed to be explored.