Exposure and Fate of Neonicotinoid Insecticides in Cocoa plantations in Ghana

Structure of thesis The results from the thesis have been presented in chapters based on various experiments conducted. These chapters are intended as manuscripts for submission to international peer reviewed journals.

Chapter 1 gives a general background to the thesis and presents pertinent literature on the topics understudy. While literature may be replete on neonicotinoids and other topics discussed in this thesis, these topics cannot be exhaustively discussed. As such, the literature most relevant to the studies conducted have been presented here. Further background and literature are presented in chapters 2 to 5 based on the study being conducted.

Chapter 2 examines the occurrence of neonicotinoid insecticide residues in diverse soil types found in cocoa farms across the entire cocoa-growing belt of Ghana. Optimization of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure for analysis of neonicotinoids in the soils being studied is discussed.

Chapter 3 presents result of analysis of applied neonicotinoid insecticide residues in cocoa beans obtained from cocoa farms across Ghana. The methodology employed in the analysis of residues in the complex matrix of cocoa beans with high fat and high pigments is described. The distribution of insecticides in cocoa shells and nibs (de-shelled beans) is also examined.

Chapter 4 describes a study of dissipation and persistence of the two most widely used neonicotinoids (imidacloprid and thiamethoxam) in representative soils from cocoa farms in Ghana. Confirmation of dissipation rates were performed using deuterated compounds of each of the insecticides studied concurrently. Estimated half-lives were obtained by use of established pesticide degradation kinetic models. xviii

Chapter 5 presents an assessment of the sorption and desorption behavior of neonicotinoids in representative soil types. The influence of soil properties, potential mobility, and leaching of neonicotinoids in the environment is discussed.

Chapter 6 summarizes the main findings from the thesis and assesses its implications for cocoa production, pesticide usage and policy in Ghana. Perspectives and further research needs are presented. 2.5 Models of information literacy for teacher development training