Ten-fold enhancement of 2,4-D effect on water hyacinth by addition of gibberellic acid

Summary Under greenhouse conditions the effective concentration of 2,4-D (amine salt) for killing water hyacinths could be decreased 10 times if 2,4-D was applied in combination with extremely low concentrations of gibberellic acid (6 g/ha or higher). This implies that in practice the risk of harming nearby vegetation is considerably reduced, and the cost of spraying programmes might be decreased.Acknowledgment. The authors are grateful to Mr G.W. Elson from ICI for sending a sample of Berelex.