With the increasing rates of glyphosate resistance it is critical that growers target 100% weed control. Focussing on rate, timing, application and stress in conjunction with using the best performing glyphosate formulations has the best chance of achieving 100% control. 90% control is no longer acceptable. Growers who leave survivors may be creating a bigger resistance problem on their farm in the future.
Recent research indicates that in annual ryegrass the most common type of resistance is translocation resistance which can be overcome in many instances by applying a higher rate of a good quality glyphosate.
One often overlooked glyphosate performance driver is the surfactant contained in glyphosate formulations. It’s well documented that glyphosate alone is very poor at penetrating leaf surfaces. As a result glyphosate formulations are manufactured with surfactants.
Surfactants facilitate the movement of glyphosate across the plant cuticle in addition to reducing the surface tension of spray droplets. According to A. Somervaille of Jubilee Consulting, generally surfactants manufactured in glyphosate formulations are much more efficient in facilitating glyphosate uptake when compared to common wetting agents added at the point of spray preparation.
Reputable brands of glyphosate, such as Roundup ULTRAMAX are developed by field testing various surfactant systems at differing concentrations in a wide range of field trial conditions. In the competitive glyphosate market many generic suppliers choose to lower surfactant loadings and/or add cheaper surfactant types, such as alkyl betaines. These cheaper surfactant systems may not offer consistent control across common weed types, particularly in challenging environmental conditions.
If glyphosate is the bullet, then the surfactant system is the gun. The better the gun the better the control.
