Improved control of purple nutsedge (Cyperus rotundus) using plant growth regulators

Purple nutsedge (Cyperus rotundus), a world-wide troublesome weed, propagates by forming a large number of subterranean organs - rhizomes, tubers and basal bulbs which develop into shoots. An attempt was made to modify the nutsedge growth habit and increase its sensitivity to herbicides. A mixture of plant growth regulators (PGR), gibberellic acid and cytokinin, was applied with and without postemergence herbicides on young nutsedge shoots. Under controlled environments, a minimum of two successive applications of PGR were needed to prevent tuber formation. Field experiments have shown that the PGR mixture applied twice after nutsedge emergence, reversed the response of rhizomes from dia-, plagio-, and ortho-gravitropic growth into a negative one, to form above-ground shoots. Under such condition, virtually no tubers were formed. PGR-treated nutsedge plants were more sensitive to postemergence application of either paraquat, MSMA, glyphosate or bentazone, as compared to PGR-untreated plants. These results open new possibilities to facilitate the control of this noxious weed.