Biopesticides are formulated microorganisms such as bacteria, fungi, viruses, or more complex organisms such as protozoa and nematodes. While several commercial products based on microorganisms have been developed and registered under the Environmental Protection Agency (EPA), actual use of these biocontrol agents for protection of crops against insects, weeds, and plant pathogens has been limited and accounts for less than 2% of total pesticide use today. Factors contributing to this low usage include costly and inefficient production methods (especially for fungi and viruses), poor storage stability, and susceptibility to environmental degradation. These are caused by exposure to temperature and pH extremes, desiccation, moisture, proteolytic enzyme activity from both plants and resident microbes, and ultraviolet (UV) radiation. Other factors contributing to the limited usage of biopesticides are: susceptibility only at specific development stage of target pest or weed, slow action for infectivity and mortality, requirement for specific environmental conditions for efficacy, and need for thorough spray coverage. Despite these limitations, industry is commited to the development of biopesticides as environmentally friendly alternatives to synthetic chemicals. This may be the result of public concern and demand to significantly reduce or even eliminate the pesticide residues in the food chain, rapid and excessive development of pest and disease resistance to chemicals, and high costs associated with the development and registration of a new chemical active ingredient.

Significant progress in formulation and application method has been made to protect the biopesticides from environmental degradation. These developments include: non-aqueous formulations, incorporation of UV protectants, starch and sodium alginate encapsulation, and adjuvants for wash-off resistance, humectancy, increased infectivity, and enhanced activity. In addition, genetic engineering technologies, such as bioencapsulation and transgenic plants have been designed to protect and extend the activity of Bacillus thuringiensis. This paper will review the work done in the area of formulations and delivery systems to enhance and extend activity of biopesticides. Primary emphasis will be on Bacillus thuringiensis, which represents more than 90% of today's biopesticide market for agronomic crops, forestry, and aquatic pest control.