TIPWG Newsletter May/June: Newsflash: Water affects pesticide performance!

By Ferdie Jordaan

Ultimately, each sprayed droplet containing a pesticide represents what was originally put into the spray tank, with water making up 90% or more of the spray mix. Don’t be mistaken: each droplet counts!

Water, with good reason, is the most obvious carrier for pesticide applications. A pesticide application to a target pest, be it plant foliage, insects or disease, relies on pesticide molecules in water droplets to transfer to the intended target. The effective transfer process of any given pesticide application depends on:

  • A reliable supply of good quality water.
  • Using the correct adjuvants to enhance the efficacy – whether they are used as an additive in the spray mixture or formulated into the finished product.
  • Selecting the right product for the purpose, meaning that the pest – plant, disease or insect – was identified correctly.
  • Determining the correct dosage for the situation.
  • Measuring the product accurately during the mixing process.
  • Ensuring uniform application of the spray mixture with calibrated spraying equipment under favourable environmental conditions.

Users often under-appreciate or even ignore water quality and yet, the properties of water in the spray tank that acts as the carrier for the pesticide can significantly affect how well those pesticides will perform. It is surprising that so few end-users bother to test for water quality (as measured by aspects such as turbidity, pH, salinity and hardness), even though it constitutes between 50 and 99% of the spray mix! Water quality may influence spray quality and determine how a pesticide interacts with the atmosphere and how it behaves on the target pest surface. How can water’s properties not be critical to success?

However, all water is not created equal
Water sampled from different sources (and even the same source from one season to the next) may differ in terms of their:

  • molecular
  • chemical, and
  • physical attributes.

For better or worse, water will affect pesticide performance. It is better to deal with it sooner rather than later. Prevention is better than the costly, follow-up, corrective treatments.

Understanding effective pesticide application requires a better understanding of what a spray droplet consists of and how those particular properties may affect results once the droplet is exposed to the atmosphere and a waxy or hairy leaf surface. Retention and absorption of the spray deposit on the pest or plant surface as well as the chemical composition of every spray droplet will, in the end, determine the effectiveness of any pesticide application.

To learn more about the ways water affects pesticide properties – read the article in full in the next issue of TIP-Mag coming soon!

/ Pesticide interest piece