Using Soap or Surfactant to Increase Pesticide Efficiency

By Aubie Keesee

Hughes County Extension Educator Ag / 4-H / CED

Adjuvant (Surfactants, stickers, spreaders, drift control) are materials that are added to your sprayer tank to increase the effectiveness of the pesticide you are using. How many times have you heard that “soap works just as well”? Well, it might help, but most won’t work as well. First, although soaps are essentially surfactants, they are not as concentrated as surfactants manufactured for use with agricultural pesticides. Household soaps usually have 10- 20% surfactant while Ag. Surfactant has a concentration of 50 to 90 %. This can make a big difference when it comes to enhancing the effectiveness of pesticide activity. Household soaps can also create problems with excessive foaming in the tank and some of these soaps will react with hard water to produce scum and precipitants that can affect pesticide performance. On the other hand most Ag. Surfactants were developed to work in sprayer tank conditions and are not as foamy and will not react with hard water.

Surfactants, or surface acting agents are most often used with herbicides to help a pesticide spread over and penetrate the waxy cuticle of the leaf or to penetrate through the small hairs present on the leaf surface. Since water has a high surface tension it tends to maintain its round, droplet shape when sitting on the surface of the leaf. The surfactant acts to break down this surface tension of the droplet allowing the liquid to spread over the leaf surface. This results in more of the pesticide coming into contact with the leaf and as a result, more of the pesticide gets into the plant.

When you are considering using a surfactant, always consult the label as to the kind of surfactant recommended and to when its addition to the pesticide will help in enhancing the control of the pesticide. Most pesticide companies have spent several years studying how surfactants work with their products and know a lot better than we can guess as to what surfactant will work best with their product.

More information on this subject can be obtained by contacting the Hughes County office of the Oklahoma Cooperative Extension Service at (405) 379-5470. 

Oklahoma State University, U. S. Department of Agriculture, State and Local Governments Cooperating:  The Oklahoma Cooperative Extension Service offers its programs to all eligible persons regardless of race, color, national origin, religion, sex, age, disability, or status as a veteran, and is an equal opportunity employer.