Screening analytical methods for the evaluation of spreadability of agrochemical tank mixture on soybean leaves

The spreadability of agrochemical tank mixture on plant leaves is crucial for the efficacy of pesticides, as it directly influences the coverage and adhesion of the active ingredients. Understanding these properties can lead to more effective pest control and reduced chemical usage. In this study, the spreadability of ten agrochemical tank mixture on soybean leaves was investigated. The contact angle between the spray and the soybean leaf was measured over time using an OCA 15 EC tensiometer, while the dynamic surface tension of the spray was assessed with a BP100 tensiometer. The static surface tension was obtained using a K100 tensiometer with the Wilhelmy plate method. All measurements were conducted at (25 ± 1)°C. The results indicate significant variations in spreadability depending on the formulation of the agrochemical tank mixture. Notably, samples with lower induction times (approximately 1 ms) and surface tensions (< 60 mN/m) at a surface age of 10 ms exhibited better spreadability and higher work of adhesion (> 45 mJ/m²). Lower surface tension leads to the formation of more small droplets, enhancing droplet coverage and density on leaves; nevertheless, this can also increase the likelihood of droplet drift and evaporation¹. These results highlight the importance of using these techniques for preliminary screening of spray formulations before field tests.

1. Zhao, R. et al. Pest Management Science 2022, 78 (6), 2512–2522.