SYMPOSIA PAPER Published: 01 January 1996

Relationship Between Spray Droplet Spread and Herbicide Phytotoxicity


Experiments were conducted to determine the relationship between spray droplet spread and herbicide phytotoxicity when secondary alcohol ethoxylate (SAEO) surfactants were used as spray adjuvants. Plant species evaluated were barley and green foxtail (grass species) and kochia and redroot pigweed (broadleaf species). Herbicides evaluated were sethoxydim (Poast®) and glyphosate (Honcho® and Roundup®). C11–15 SAEO surfactants evaluated had hydrophilic:lipophilic balance (HLB) values from 8 to 18. Spray droplet spread on adaxial leaf surface was greater with surfactants having low (8 to 12.1) compared to high (15.4 to 18) HLB values. Droplet spread appeared related to epicuticular wax structure. Droplet spread was greater on microcrystalline epicuticular waxes (barley, green foxtail, and kochia) than on amorphous epicuticular waxes (redroot pigweed). The presence of herbicide affected spray droplet spread on leaf surfaces. Phytotoxicity was greatest when Poast® was applied with surfactants having HLB values 13.3 to 16.3, and when Honcho® and Roundup® were applied with surfactants having HLB values of 17.4 to 18. Efficacy of Honcho® and Roundup® was negatively correlated with droplet spread, while the efficacy of Poast® did not correlate with droplet spread.

Author Information

Manthey, FA
North Dakota State University, Fargo, ND
Szelezniak, EF
North Dakota State University, Fargo, ND
Nalewaja, JD
North Dakota State University, Fargo, ND
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Developed by Committee: E35
Pages: 182–191
DOI: 10.1520/STP11350S
ISBN-EB: 978-0-8031-5346-2
ISBN-13: 978-0-8031-2035-8