Biological control is a plant protection strategy widely-used in horticultural cropping systems to regulate insect and mite pest populations on greenhouse-grown ornamentals and vegetables. The use of natural enemies in controlling the SWD has been researched in Chapter One. Chapter Two aims to recover the history and present the current status of the biological control of fruit flies of the genus Anastrepha and to show perspectives of the use of such method. Chapter Three discusses the advantages and issues affiliated with using natural enemies in conjunction with pesticides and provides insights on the practicality of using both plant protection strategies simultaneously. Chapter Four describes screening methods for candidate biocontrol agents, application methods and challenges associated with biological control of fungal pathogens by antagonistic microorganisms.