In agricultural product formulation development, adjuvants are used to ensure the formulation possesses favorable attributes for fully exploiting the efficacy potential of the active ingredient, good compatibility, acceptable leaf coverage, excellent rain fastness, and so forth. While whole formulations are routinely tested with crop species, we do not possess a good picture of the relative properties of these adjuvants on their own. We used live plant leaves with different modified surfaces to assess attributes of adjuvants in an innovative and cost-effective way. Data sets were collected for some typical adjuvants by testing each at several concentrations on both modified and unmodified plant leaves. Waxy surface represents most of the global crop and weed surfaces, and the surface modification technique allow us to adjust the surface to different hydrophobicity. Some hydrophobic leaves are difficult to wet due to dense coverage of crystalline surface waxes, and cereal surface is a good example for such hydrophobic leaf surfaces. Using one such plant species with a cuticle tough enough to allow stripping of waxes with cellulose acetate, we were able to modify it to a smooth moderate lipophilic surface. The film stripping technique offers the advantages of speed, simplicity and versatility for the hydrophobicity modification. The different hydrophobicity was confirmed and measured by contact angle. The correlation of surface hydrophobicity modification with treatment time and solution concentration were investigated. Based on the surface modification properties, we were able to assess and rank the adjuvants based on their performance in each following experiments. In particular, assessment of droplet behavior on the leaf surfaces was investigated. The addition of a fluorescent dye in the adjuvant solutions was quantified by image analysis process. The detailed information on droplet retention, spreading and rainfastness information and other adjuvant attributes contribute to even more sound decisions when developing formulations.

Using surface modified leaves as a model to assess attributes of adjuvants used with agrochemical formulations

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