This monograph contains four chapters, each of which provides a different perspective on biopesticides. Chapter One concerns the use of biopesticides in sustainable agriculture, including the interactions between biopesticides and chemical pesticides, production issues, and opportunities for future research. Chapter Two describes the bottom-up approach for using Bacillus thuringiensis (Bt) as a biopesticide and for enhancing host plant resistance against major foliage feeders through deployment of suitable cry genes. Chapter Three reviews strategies for mitigating the spread of Bt resistance and improving insecticidal activity against Bt-susceptible pests. Lastly, Chapter Four aims to revise, debate, and evaluate the effects of Bt as phosphate solubilizing and phosphorus uptake by plant establishment.