ADJUVANTS
This is a supplementary part of the Herbicidal Control page of
this web site.
ADJUVANTS
This is a supplementary part of the Herbicidal Control page of
this web site.
For more than a century, pesticide applicators have mixed adjuvants into their herbicide spray tanks in order to facilitate or modify the action of the applied chemical, and make the herbicide application more effective.
Like the water that is mixed with most aquatic herbicides, these commercial additives carry the herbicide, causing the herbicide to spray with less drift, stick to the leaves better, spread more evenly over the plant, and so on. The earliest adjuvants were made from whale oils that were meant to enable a chemical to stick to the targeted species. In the mid-twentieth century, soaps and detergents were popular adjuvants. Research in the 1950's led to the development of more sophisticated adjuvants.
Today several manufactured herbicides contain specially formulated adjuvants already mixed into the herbicide container. Often, herbicide applicators themselves select and mix adjuvants with the chemicals they intend to use in order to tailor the herbicide application to their specific needs.
Far from the whale oils used in the early days, contemporary adjuvants are made from complex synthetic formulations that are designed for specific purposes. Unlike the chemical herbicides they are added to, most modern adjuvants are inert and have no toxic effect on the plants or the environment.
In the U.S., there are several hundred name brand adjuvants that have various effects on aquatic herbicides. Adjuvants do not require EPA or Florida Department of Agriculture and Consumer Services testing in order to be used.
In general, adjuvants can be classified into three categories:
Activator adjuvants increase the effectiveness of the herbicide by altering the:
Surfactants (surface-active agent) promote the penetration of the chemical into the leaves of the plant.Spray-modifier adjuvants affect the delivery and placement of the spray solution. They make the herbicide spray easier to aim, reduce herbicide drift in the air, and cause the spray to more readily adhere to the plant.Wetting agents increase the ability of water to displace air or liquid from the plant's surface so the herbicide will spread more evenly over the plant.
Oils increase the retention time of the sprayed material on the plant and enhance uptake though the leaf surface.
Stickers and spreaders are made of gels, oils, and waxes that help spread and adhere herbicide spray droplets to foliage.Utility-modifier adjuvants make the herbicide more useful in certain environmental conditions.Foams make it easier to control drift--so the herbicide is less likely to be misapplied.
Polymers are also used for drift control and to help break surface tension on the water, thus enabling the herbicide to sink onto submersed aquatic weeds.
Inverting oils form a viscous blend that reduces drift during application, increases contact time on the plant, and sinks the herbicide onto submersed plants.
Buffering agents help to disperse the herbicide in alkaline or acidic water.Anti-foam agents enable the herbicides to mix with soft water.
When used properly, adjuvants are relatively harmless compounds that can enhance herbicidal properties and decrease the overall quantity of chemicals needed for plant control. Yet, recent studies have indicated that some adjuvants, primarily surfactants, can impact fish and aquatic vertebrates. Although many manufactured herbicides already contain adjuvants and provide application information on the label, each plant management project is unique and requires an assessment by a professional plant manager before the appropriate adjuvant can be selected and utilized.
For more information, see the online version of the Compendium of Herbicide Adjuvants, 6th Edition by Bryan Young, Southern Illinois University, Carbondale.
This page was authored by Sarah Cervone
with research assistance by Becca Hassell.
Data is from the APIRS
Database.
This page was designed and is managed by Becca Hassell.
Photography and graphics are by Ann Murray and Vic Ramey.
Vic Ramey is the editor.
DEP review by Jeff Schardt and Judy Ludlow.
A collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Invasive Plant Management Section of the Florida Fish and Wildlife Conservation Commission.
