Brazilian egeria herbicide mesocosm and field trials for managing the Sacramento–San Joaquin River Delta

• Published in: Journal of aquatic plant management Vol. 59; pp. 90 - 97
• Main Authors: Madsen, John D, Morgan, Christy, Miskella, John, Kyser, Guy, Gilbert, Patricia, O'Brien, Jon, Getsinger, Kurt D
• Format: Journal Article
• Language: English
• Published: Gainesville Aquatic Plant Management Society, Inc 01.01.2021
• Subjects: Agriculture; Algae; Aquatic plants; Biomass; Canals; Copper; Diquat; Endangered & extinct species; Endangered animals; Endangered plants; Endangered species; Ethylenediamine; Fish; Flowers & plants; Herbicides; Indigenous plants; Indigenous species; Mesocosms; Plant species; Potassium; Potassium chromate; Potassium chromates; Potassium salts; Rare species; Reduction; Rice; Rivers; Salt; Salts; Sodium; Statistical analysis; Tanks; Weeds; San Joaquin River Delta; Sacramento California; United States > US; Japan; Brazil; California; Florida; North America
• ISSN: 0146-6623

The nonnative Brazilian egeria (Egeria densa Planch.) is the dominant submersed plant in the Sacramento-San Joaquin River Delta, displacing native plant species and degrading habitat for endangered fish species. A mesocosm study was conducted at the U.S. Department of Agriculture (USDA) facility in Davis, CA to determine efficacy of aquatic herbicides on egeria. Fifty mesocosm tanks of 167 L capacity were planted with four 4.2-L pots of egeria. Four tanks each were treated with bispyribac sodium (45 pg L-1), carfentrazone-ethyl (200 pg L-1), ethylenediamine chelate of copper (1,000 pg L '), diquat (390 pg L1), dipotassium salt of endothall (5,000 pg L-1), dimethylalkylamine salt of endothall (5,000 pg L- ), florpyrauxifen-benzyl (50 pg L- ), flumioxazin (400 pg L '), fluridone (60 pg L '), imazamox (500 pg L '), penoxsulam (60 pg L-1), and four tanks were left as an untreated reference. All were single treatments, static exposures for 10 wk. At the end of 10 wk, all pots were harvested, and the shoots were dried at 70 C for 48 h. All herbicides produced some statistically significant reduction in biomass. Copper, diquat, endothall dimethylalkylamine, and fluridone produced > 90% control. Carfentrazone (69%) and the potassium salt of endothall (62%) provided greater than 50% control, with other herbicides producing somewhat less than 50% control. Field demonstration has substantiated some of these findings. A study of three treatment plots in 2016 found an 85% reduction in biomass in fluridone-treated plots, compared to a 26% increase in biomass in untreated plots. A field trial on two plots treated with diquat found 98% and 80% control, respectively. A field trial with the dipotassium salt of endothall resulted in 43% control after one treatment.