SYMPOSIA PAPER Published: 01 January 2001

Influence of Three Experimental Adjuvants on Glyphosate Weed Efficacy


Many agricultural spray adjuvants utilize one or more organosilicone surfactants in their composition. These materials have been shown to provide biological efficacy enhancement to agrichemicals and/or correct spray application problems. Commercial adjuvant products that utilize organosilicone surfactants are currently formulated only as liquid products.

In recent years, many pesticide products have been introduced as dry formulations. These formulations have provided growers and applicators with the advantages of reduced exposure, improved storage stability and easier package disposal. Until now, the technology necessary to produce dry adjuvants utilizing organosilicone surfactants has been unavailable.

Two formulation technologies now provide the option for developing dry organosilicone spray adjuvant products; a.) dry co-surfactant blends of organosilicone and propylene oxide/ethylene oxide copolymers and b.) organosilicone impregnated on dry carboxylic acid salts. Laboratory evaluations, regarding the surface chemistry properties of these dry organosilicone adjuvants, compare favorably with those from the traditional liquid formulations. The purpose of this research was to determine if glyphosate efficacy enhancement provided by dry organosilicone based adjuvant products, is comparable to control levels of liquid organosilicone based adjuvant with glyphosate and to evaluate the impact of dry surfactant formulation variables. The field efficacy experiments were conducted at eight locations in the northern and southern regions of the United States, to evaluate glyphosate activity on various annual and perennial weed species. The experimental adjuvants were tank mixed with a glyphosate formulation that did not contain surfactant. A 731 mL/ha rate of glyphosate was applied at seven of the sites, with one location having had al462 mL/ha rate applied.

HM9208-A and HM9507 (dry formulations of organosilicone surfactants), were applied 453.6 grams/379 liters of spray solution. HM9220 (a liquid formulation of organosilicone surfactant), was applied at 0.125% v/v concentration. All treatments were applied at 94 L/ha spray volume. Applications to quackgrass, perennial ryegrass, rhizome johnsongrass, alfalfa and annual fleabane resulted in greater levels of weed control due to the addition of HM9208-A versus HM9507 or HM9220. Applications to Timothygrass resulted in equivalent control levels among the three adjuvants. At a site in Mississippi, glyphosate plus HM9208-A provided better control of goosegrass and southwestern cupgrass when compared to the addition of HM9507. Control levels were equivalent on these two weed species with either HM9208-A or HM9220.

Author Information

Roberts, JR
Helena Chemical Company, Memphis, TN
Mack, RE
Helena Chemical Company, Memphis, TN
Baker, TA
Helena Chemical Company, Memphis, TN
Price: $25.00
Contact Sales
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Developed by Committee: E35
Pages: 95–102
DOI: 10.1520/STP10437S
ISBN-EB: 978-0-8031-5451-3
ISBN-13: 978-0-8031-2877-4