Effective pesticide applications require attention to factors that influence product performance such as product selection, label instructions, equipment calibration and application timing. A factor that doesn’t get much attention is the quality of the water used to spray the product. Water often comprises ninety-five percent (or more) of the spray solution. Research clearly shows that the quality of water used for spraying can affect how pesticides perform. Its effect on product efficacy is reflected in the success of your spray operation.
So why is it that we seldom notice something as obvious as the quality of water used in the spray tank? For the most part, water is viewed as a relatively clean input; if it runs clear, we don’t give much thought to its purity. What kinds of problems can poor water quality cause? Water quality factors, such as acidity and dissolved minerals, can interact with the active and/or additive ingredients of the pesticide product. Poor water quality can adversely influence results by reducing solubility and decreasing absorption by the target pest, resulting in inferior performance and the need for re-treatment.
Reduced product performance may not be obvious. In some cases, the influence of water on the pesticide reduces its effectiveness only slightly, enough that tolerant or tough-to-control weeds, insects, and diseases are not well controlled. An applicator might blame the pesticide, add another product to the tank mix, blame other factors for lack of performance (e.g., weather, resistance), or increase the application rate, thereby masking the effect of the water on the product’s performance.
With all of the variables surrounding water as a carrier, how important are adjuvants? Thomas Jordan, Purdue Extension Weed Specialist defined the importance of adjuvants in managing variables of water as a carrier, “Adjuvants, often misunderstood by the customer, are materials that facilitate the activity of herbicides, insecticides or fungicides and modify characteristics to improve consistent performance.” Dr. Richard Zollinger, NDSU Weed Science also adds, “Do not eliminate adjuvants or cut back recommended adjuvant rates; it may work sometimes, but in the long run it is not worth it. Cutting back adjuvant rates is probably the biggest weed-control issue today.” Overlooking the importance of water quality could be the little factor that makes a big difference.