Herbicides for management of waterhyacinth in the Sacramento-San Joaquin River Delta, California

• Published in: Journal of aquatic plant management 2020-07, Vol.58 (2), p.98-104
• Main Authors: Madsen, John D, Kyser, Guy B
• Format: Article
• Language: English
• Subjects: 2,4-D; Agricultural practices; Aquatic plants; Aquatic weeds; Biomass; Chemical pest control; Constrictions; Endangered species; Freshwater plants; Glyphosate; Herbicide resistance; Herbicides; Integrated pest management; Irrigation water; Maintenance management; Pest control; Pesticides; Protection and preservation; Rare species; Restrictions; Rivers; Seeds; Stewardship; Water transportation; Wildlife conservation
• ISSN: 0146-6623

Waterhyacinth (Eichhornia crassipes (Mart.) Solms) is a global aquatic weed. Although a number of herbicides such as 2,4-D and glyphosate effectively control this plant, additional herbicides need to be evaluated to address concerns for herbicide stewardship and environmental restrictions on the use of herbicides in particular areas. Waterhyacinth has become a significant nuisance in the Sacramento-San Joaquin River Delta. The predominant herbicides for management of waterhyacinth in the Delta have been 2,4-D and glyphosate. However, environmental restrictions related to irrigation water residues and restrictions for preservation of endangered species are prompting consideration of the new reduced-risk herbicides imazamox and penoxsulam. Two trials were performed in floating quadrats in the Delta during the summer of 2016. In the first trial, two rates each of 2,4-D, glyphosate, imazamox, and penoxsulam were treated in four replicate quadrats. In this trial, the highest rates of all four herbicides provided greater than 80% control (2,4-D, 82%; glyphosate, 87%; imazamox, 93%; and penoxsulam, 94%). In the second trial, the lower rate of glyphosate (1,681 g a.e. [ha.sup.-1]) was compared to four rates each of imazamox (187 to 1,494 g a.i. [ha.sup.-1]) and penoxsulam (12 to 98 g a.i. [ha.sup.-1]). In this trial, the highest rates of imazamox and penoxsulam provided 96 and 95% control, respectively, compared to the untreated reference. Imazamox and penoxsulam will provide suitable control of waterhyacinth as part of an operational program and may be used as part of an integrated pest management program with considerations of herbicide resistance management. In addition, incorporating these reduced-risk herbicides into the management program can reduce the amount of pesticides applied per acre to achieve waterhyacinth control. Key words: Eichhornia crassipes (Mart.) Solms, Glyphosate, Imazamox, Penoxsulam, 2,4-D