Copper (Cu) has been used extensively as a crop protectant by the agriculture industry. Cu sulfate was introduced in 1761 as a fungicide to protect seeds. The Bordeaux and Burgundy mixtures, combinations of Cu with lime and soda ash, respectively, were introduced in 1880s. Since then, for many decades, Cu hydroxide, Cu oxide and Cu oxychloride have been widely used. However, such extensive use of Cu in agriculture has contributed to ecotoxicity, negatively impacting soil microbiomes and aquatic species. Soil accumulation of Cu has detrimental effect on plants as excess amounts of Cu not only increases the phytotoxicity risks but can also limit the uptake on essential micronutrients such as Zinc (Zn). Moreover, many plant pathogens have developed resistance to Cu over the years. For instance, bacterial spot disease of tomato, pepper and peach, caused by Xanthomonas species experiencing alarming increase of Cu tolerance. This disease can no longer be effectively controlled with current commercial formulations. Yield loses are affecting the multi-billion-dollar industry in the USA alone. In 2017, the US Environmental Protection Agency (EPA) has released a new recommendation aiming to reduce Cu application rates for certain specialty crop growers, recognizing the alarming level of Cu in soil. In the absence of suitable alternatives, growers affected by this measure will face challenges to protect their crops in coming years. Therefore, there is a desperate need for developing advanced bactericide formulations to reduce Cu usage without compromising the field efficacy. The goal of this doctoral dissertation research is to develop advanced bactericide formulations using nanotechnology to reduce Cu usage. Part I of this dissertation introduces a novel concept of locally-systemic pesticide (LSP) particles. The LSP design, comprises two antimicrobial active ingredients (A.I.s) integrated into a single nanoparticle system. LSP has a core-shell structure loaded with antimicrobial Cu and Quaternary Ammonium compound (Quat). Effect of LSP particle size on Cu release and rainfastness was investigated, as well as their plant injury potential and antimicrobial efficacy against selected pathogens. In all aspects, the LSP demonstrated superior performance compared to Cu standard conventionally used by growers. Part II of this dissertation deals with an alternative to Cu bactericide using nanoparticle of Zinc Oxide (ZnO). The objective is to develop a systemic ZnO based bactericide that will deliver antimicrobial Zn to plant vascular tissue such as xylem and phloem for controlling vascular diseases such as Pierce's disease in grapes and Huanglongbing (HLB) in citrus, also known as citrus greening. In collaboration with partners in the agrochemical industry, agricultural-grade ZinkicideTM product formulation was developed, optimized and characterized. Zinkicide contains ultra-small size ( < 5.0 nm) ZnO particles and it is designed to be fully degraded to release micronutrient Zn ions. Performance of Zinkicide was evaluated against Cu products conventionally used by growers. In all aspects, Zinkicide demonstrated superior efficacy against model pathogens tested than Cu standards, suggesting its potential for use as a Cu alternative.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Ozcan, Ali, "Advanced Multifunctional Bactericides for Crop Protection: A New Strategy to Reduce Cu Pesticide Footprint in the Environment" (2019). Electronic Theses and Dissertations, 2004-2019. 6860.