VIM. CONTROL OF AQUATIC WEEDS 



FLOATING WEEDS 



(1) For control of water -hyacinth and waterlettuce : Amine or low-volatile 

 ester of 2,4-D at 1 to 4 pounds in 2 to 150 gallons of water per acre. Spray 

 at low pressure with large nozzles to reduce spray drift. Use oil, or an 

 oil-water emulsion in spraying waterlettuce to insure proper wetting of 

 the leaves. 



SUBMERSED WEEDS 

 In Irrigation and Drainage Canals 



(1) For control of rooted submersed species (such as pondweeds and 

 waterweed in Western and Great Plains irrigated areas): Emulsifiable 

 aromatic solvents (methylated benzenes such as Xylene) applied in canal 

 at 400 to 740 p. p.m., which is 5.4 to 10 gallons per c.f.s. (cubic feet per 

 second) of water flow, during a 30-minute period. More than one treat- 

 ment may be necessary in regions with long growing seasons. For de- 

 tailed recommendations on use of this method, see USDA Circular No. 

 971, "The Use of Aromatic Solvents for Control of Submersed Aquatic 

 Weeds in Irrigation Channels." 



(2) For control of rooted submersed species (such as southern naiad, 

 coontail, and bladderwort in Southeastern States): Use emulsifiable 

 aromatic solvents at 20 to 200 p. p.m. during a continuous treatment period 

 of 24 to 48 hours. Gasoline mixtures with polychlorobenzenes at similar 

 concentrations and exposure times have given good control in Florida 

 tests. Water temperature and movement influences the rate of treatment 

 and exposure time. The warmer water and quasi- static water conditions 

 prevalent in water control canals of Southeastern States permit much 

 longer treatment exposure times and make possible control of waterweeds 

 with much lower concentrations of herbicides than are necessary in colder 

 and rapidly flowing water conditions in canals of Western and Great Plains 

 States. 



(3) For control of filamentous green and red algae (in water flowing at 

 a velocity of 0.5 foot or more per second): Apply copper sulfate at 10 to 

 12 p. p.m. during a continuous treatment period of 30 minutes. Rosin amine 

 D acetate (RADA) at 10 to 12 p. p.m. applied in canal for 30 minutes has 

 satisfactorily controlled red algae and, in some situations, green algae. 

 Treatments of either copper sulfate or RADA usually must be repeated at 

 intervals of 2 to 6 weeks to maintain adequate control of algae. Aromatic 

 solvents at 100 to 150 p. p.m. applied during a 15-minute period have 

 satisfactorily controlled filamentous green algae in Western irrigation 

 canals. 



In Reservoirs and Large Canals Carrying Water for Potable or Industrial 

 Uses or for Irrigation 



(1) For control of algae or rooted submersed aquatic species in slowly 

 moving water : Copper sulfate applied continuously in sufficient quantity to 

 maintain 0.6 to 1.0 p. p.m. concentration in the water throughout the growing 

 season for aquatic weeds. The concentration should be maintained at 1.0 

 p. p.m. early in the season. It may be reduced gradually after midsummer 



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