Living systems as natural crop-protection agents

The concept of using living natural systems for crop protection is not nove l. Regulatory pressures leading to decreased availability of chemical pesti cides and increased awareness of possible adverse toxicological effects of some traditional chemicals have resulted in the search for safer alternativ es. Additionally, resistance and pest resurgence issues, together with the introduction of newer, active molecules of biological origin or the synthet ic derivatives thereof, have renewed the interest in living systems. While the main thrust in biological pesticide development to date has been in the area of insecticides, primarily driven by the development of Bacillus thur ingiensis-based insecticides, the last decade has seen several attempts at identification and development of fungicidal, nematicidal and herbicidal pr oducts. Nevertheless, natural products occupy a relatively small niche in t he overall US$32 billion global agricultural pesticide market. Living systems used in practical agriculture comprise bacteria, fungi, viru ses, plants or plant-derived products (botanicals), and pathogen/predator s ystems. From a commercial perspective, however, the list is short and gener ally Limited to those bacterial or fungal agents which are amenable to scal ed-up production, and to those that consistently provide benefits and finan cial returns to the grower. Significant basic research has been carried out by many academic and public research groups in these areas, notable techni cal advances on basic and applied aspects of these organisms have also been made at industrial laboratories. While specific issues relating to individ ual biocontrol agents may differ, the information available, based on the d evelopment of Bacillus thuringiensis-based biological insecticides, has pro vided the highest degree of basic understanding on all commercial aspects o f microbial pesticides. This paper addresses the current status of the use of biological agents to improve agricultural productivity, giving particula r attention to their capabilities, critical factors and limitations, and is an attempt to review the recent trends in the light of advances in genetic engineering technology. Biotechnology has provided newer approaches to altering toxins for improved specificity to target pests, increased potency, and to enhancing expressio n and delivery mechanisms. Several research groups have utilized biotechnol ogy to harness the potential of these natural agents. The recent introducti on of transgenic plant technology, while presenting a powerful new option f or exploiting the natural biological resources for controlling pests, if no t managed, can potentially develop into a 'Pandora's box' and result in iss ues that might eventually threaten the commercial use of certain Living sys tems. Thus, as the newer technologies appear on the horizon, it becomes inh erently important to recognize the limitations and capabilities of each pes t management tool in different agricultural systems. (C) 2000 Society of Ch emical Industry.