Chemical control of aquatic weed water hyacinth (Eichhornia crassipes)

Water hyacinth (Eichhornia crassipes (Mart.) Solms)is the most important invasive aquatic weed in the world. This plant has expanded widely in aquatic habitats in the north of Iran in less than a decade after introduction. To introduce herbicides for chemical control of this weed, two pot experiments were conducted at the Rice Research Institute of Iran in 2017 and 2018. The purpose of the first experiment was to screen herbicides to identify effective herbicides for water hyacinth control. Results showed that among 21 studied herbicides, 15 herbicides had less than 16% and 6 herbicides had more than 30% efficacy on water hyacinth control. The second experiment was performed with the most effective herbicides in the first experiment and with the dose studied in the first experiment and double dose. The results showed that the efficacy of U46-Difloid (2,4-D, SL 72%, 2160 g ai/ha), U46-Combifloid (2,4-D+MCPA, SL 67.5%, 2700 g ai/ha), Dialensuper (2,4-D+Dicamba, SL 46.4%, 1856 g ai/ha), Roundup (Glyphosate, SL 41%, 1640 g ai/ha), Nominee (Bispyribac sodium “BPS”, SC 10%, 50 g ai/ha) and Cleanweed (BPS, SC 40%, 80, g ai/ha) at double dose was 75, 93, 81, 93, 91 and 100% respectively. Among the investigated herbicides, the inhibitory effect of BPS (Nominee and Cleanweed) on biomass, leaf area and propagation of water hayacinth seedlings in both investigated doses was similar or more than other herbicides. Therefore, BPS as a selective herbicide for rice and authorized for aquatic ecosystems without toxicity on fish, is recommended for chemical control of water hayacinth.