Microencapsulated Clomazone: Formulation Stability, Tank Mix Volatility, and Solvent Effects

Abstract

Abstract Clomazone is microencapsulated and sold in the U.S. as a dispersion in water, a capsule suspension (CS), under the name Command®®Command is a trademark of FMC Corporation. 3ME herbicide. Our encapsulated formulation reduces the volatility of the active ingredient when it is applied to the soil surface in a typical agricultural spray use. The commercialized formulation was selected from among hundreds of encapsulated formulations for its ability to reliably control volatility. Many of the rejected formulations did not control volatility, and it was only through a careful optimization of the encapsulation process that we came to our selection. As part of our formulation development process, we developed a laboratory volatility assessment method for use in screening formulations. This method determined the volatility following a soil application and normalized the volatility of the encapsulated formulations to that of the older Command 4EC herbicide formulation. Our optimized formulation was introduced to the market in 1996 to control volatility. A sample of the first production batch of commercial clomazone 3CS formulation, which had been stored at room temperature and regularly assessed for ten years, continues to provide excellent control of volatility. This indicates that the capsules have remained intact and functional, and that the proportion of clomazone in the capsule, versus outside, has not changed as the formulation aged. When these capsules are diluted in water, some clomazone slowly diffuses out of the capsules. This release is limited by the water solubility of clomazone. Even for excessive residence times in the spray tank, the volatility from the soil surface increased only slightly and was well within the acceptable range, for dilutions used for agricultural spray application. Improper addition of solvents and surfactants to the formulation can provide a phase where the clomazone is soluble, and this solubility will extract clomazone from the capsules. Under these conditions the volatility of the product increased so that it was similar to an unencapsulated formulation. In contrast, addition of other herbicides or spray additives to the spray tank mix had little impact on the volatility.