Submitted to: American Society for Testing and Materials
Publication Type: Proceedings
Publication Acceptance Date: 4/22/2003
Publication Date: N/A
Technical Abstract: The multiple role of adjuvants in spray application of systemic agrochemicals is discussed with special reference to tree fruits. The spray application process can be viewed as a series of interdependent events, namely formulation, atomization, spray transfer and interaction with the plant surface leading to retention and penetration. Adjuvants play a role in each event for they are used extensively in formulation and as a tank mix during application. They facilitate solubilization of the active ingredient and modify the physico-chemical properties of the spray solution. The size distribution of the spray may be shifted to a lower or higher VMD by surfactants and drift retardants, respectively. Spray retention and spreading is increased on difficult to wet plant surfaces. Foliar penetration can be increased by stomatal pore infiltration by surfactants that lower surface tension to <30 mN/m. Transcuticular penetration may be depressed by adjuvants that reside in the spray droplet residue solubilizing the agrochemical and effectively reducing the driving force. Other surfactants penetrate into the cuticle and plasticize the waxes leading to increased transcuticular diffusion of the active ingredient. Implications for the presence of multiple spray additives in the spray solution and droplet residue on performance of the active ingredient is stressed.