Volume 7, Issue 9 (October 2010)
Development of a Novel Solvent-Based Formulation for Pesticides That Are Prone to Crystallization
Many of today’s most widely used pesticidal active ingredients (AIs) are crystalline solids with limited solubility in commonly used aromatic or aliphatic solvent systems. Many of those solid AIs can only be dissolved at suitable concentrations in very polar or slightly water-soluble solvents, such as cyclohexanone, isophorone, N-methylpyrrolidone, etc. The disadvantage of these solvents is that when they are used as the sole dissolving agent, they can lead to the crystallization of the AI upon dilution of the formulation with water, making the effective and uniform application of the AI impossible due to nozzle and/or filter plugging. In the United States, for example, products containing the azole fungicide, tebuconazole, are therefore mainly formulated as suspension concentrates rather than emulsifiable concentrates (ECs). We have developed a novel solvent-based EC formulation, which inhibits crystal growth when used with a variety of pesticidal actives, including triazole fungicides, in their concentrated and diluted aqueous compositions. This was achieved using a composition containing a water-insoluble solvent together with other stabilizers. This composition was used to prepare formulations of pesticidal AIs with a concentration from 200 to 250 AI g/L. The crystallization of the AI is prevented by the liquid composition, whose ingredients act not only as solvents but also as crystallization inhibitors during the application of the pesticide concentrate as a diluted aqueous spray. This paper presents data on the physical stability of the concentrated formulations, as well as for diluted aqueous spray mixtures, showing that no crystals will form under simulated use conditions. Specific illustrations of this novel approach to solving the complex crystallization problems associated with the above-mentioned class of “problematic” pesticidal compounds include several tebuconazole-based EC formulations. We will also present results from field trials to show their biological performance.