By Richard Zollinger
Question: We have cattails in some areas in fields that we have not been able to seed for the last couple of years. The area is dry this year. What can you use to get rid of them?
Answer: The North Dakota Weed Guide shows the following options for cattail control:
• Glyphosate (only 4 pound active ingredient no-adjuvant formulations) at 4.5 pints of 4 pound active ingredient per gallon concentrate per acre. Add approved non-ionic surfactant at 1 quart per 100 gallons of water. Apply at early to full bloom stage in late July to mid-August.
• Arsenal + MSO adjuvant, 2 to 4 pints (1% v/v solution) per acre. Apply to cattails with green foliage after leaf elongation.
• Raptor + MSO adjuvant, 4 to 5 fluid ounces plus 1.5 pints per acre. May require retreatment.
The glyphosate work was done by Cal Messersmith, North Dakota State University weed scientist, before he retired. He found glyphosate at 4.5 pints per acre of an unloaded (4 pound active ingredient per gallon) formulation provided excellent control.
Why the “unloaded” — or “no surfactant added” — formulation? Because partial- or full-surfactant load formulations of glyphosate cannot be used in bodies of water that contain aquatic life. The surfactants in glyphosate formulations are lethal to aquatic life. A surfactant approved for use in bodies of water must be applied with unloaded glyphosate formulations. Use an approved non-ionic surfactant at 0.5% to 1% v/v (volume of reagent per final solution volume).
Messersmith’s research also showed best control occurs when glyphosate is applied in July to mid-August when cattail is in early to full bloom. The data show when vegetative cattail was sprayed on June 10, the control ranged from 12% to 16%. When sprayed to early flowering cattail on July 22, control was 51% to 91%. When sprayed on 6-foot, full flowering cattail on Aug 1, control was 92% to 100%.
Cattail is a perennial. Thus, the same motto applies to cattail as other perennial species: “Perennial species cannot be controlled with one application of any herbicide.” If you can’t wait until July or August to spray the cattail, then plan your spray activities to provide the best control with the resources you have.
Zollinger is the North Dakota State University Extension weed specialist.