SEDL / STP / STP1234-EB / STP13014S

Relation of Surfactant HLB to Glyphosate Phytotoxicity

Nalewaja, JD
Professor, Polish Exchange Scientist, Visiting Scientist, and Research Scientist, North Dakota State University, Fargo, ND

Koziara, W
Professor, Polish Exchange Scientist, Visiting Scientist, and Research Scientist, North Dakota State University, Fargo, ND

Matysiak, R
Professor, Polish Exchange Scientist, Visiting Scientist, and Research Scientist, North Dakota State University, Fargo, ND

Manthey, FA
Professor, Polish Exchange Scientist, Visiting Scientist, and Research Scientist, North Dakota State University, Fargo, ND

Pages: 9    Published: Jan 1995

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Abstract

Research was conducted to determine the phytotoxicity of glyphosate [N-(phosphonomethyl)glycine] formulations (Roundup® and Honcho®) as influenced by calcium chloride or calcium chloride plus ammonium sulfate and surfactant hydrophilic:lipophilic balance (HLB). Roundup® and Honcho® phytotoxicity to wheat generally was maximized by octylphenoxy and nonylphenoxy surfactants with HLB of 15 to 16 but to kochia phytotoxicity increased linearly with HLB except the response decreased or was quadratic in the presence of CaCl². Roundup® and Honcho® phytotoxicity to wheat increased with surfactant concentration regardless of HLB, but concentration did not overcome differences between surfactants. Surfactants within the optimum HLB range differed similarly in effectiveness with both Roundup® and Honcho®. Certain surfactant adjuvants reduced phytotoxicity to wheat by glyphosate with MON 0818, the surfactant in the Roundup® formulation. Surfactant effectiveness was dependent upon surfactant chemistry and HLB.