Iranian Society of Weed Science Iranian Journal of Weed Science 1735-3548 16 1 2020 04 20 Chemical control of aquatic weed water hyacinth (Eichhornia crassipes) Chemical control of aquatic weed water hyacinth (Eichhornia crassipes) 63 78 121535 10.22092/IJWS.2020.1601.1318 FA Bijan Yaghoubi Rice Research Institute Farzin Pouramir Assistant professor, Rice Research Institute of Iran, Rasht, Iran Fatemeh Mansourpour Expert of Rice Research Institute of Iran, Agriculture Research, Education and Extension Organization, Rasht, Iran Journal Article 2019 02 25 Water hyacinth (<em>Eichhornia crassipes</em> (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. Water hyacinth (<em>Eichhornia crassipes</em> (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. https://ijws.areeo.ac.ir/article_121535_f0f083f8249c7826339f044abf46673f.pdf