Cigarette smoke condensate (CSC) was fractionated for biological experiments examining tumorigenic activity on mouse skin. The active fractions were combined in various ways in order to determine their additive effects. Steam distillation of the ether-soluble weak acid fraction (WA
The multiple role of adjuvants in spray application of systemic agrochemicals is reviewed 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 solubilzation 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 are 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-1. Transcuticular penetration may be depressed by adjuvants that do not penetrate, but reside on the surface, in the spray droplet residue and solubilize/complex the agrochemical in micelles (or other momomer agregrates) 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 are stressed.
Spray retention by foliar targets is influenced by both biological and rheological factors. Plant morphology (leaf surface-structure, degree of pubescence, leaf angle) combined with the spray liquid properties (surface tension, viscosity, droplet sizes, and velocities) all affect spray retention and subsequent deposit formation. Techniques used to explore these phenomena include on-demand droplet generators, high-speed movies and video-imaging. Maximum bubble pressure and oscillating jet technologies allow surface tension measurements to be made at droplet surface ages consistent with the impaction process. Judicious formulating and increased use of adjuvants has created many new opportunities for manipulating spray and deposit formation. However, recently proposed tactics advocating the use of coarse sprays to reduce drift have implications for pesticide targeting and subsequent pest control. This paper focuses on what has been learned about the phenomena of impaction, retention and deposit formation and suggests that while improved retention of pesticides by target plants is both practical and achievable, pesticide use rate reductions may not be so until the relationship between retention and efficacy is better understood.
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