Bt has the capacity to kill insects by the pathogenicity of the bacterium itself, and proteinaceous (cry) toxins that form bi-pyramidal crystals inside each bacterium and constitute the main activity of products, can also act as stomach poisons to insect pests. Because of the complexity of action (which might also include a third endotoxin factor), the International Unit (IU) was developed based on bioassay measurements against a standard, although there can be some confusion about their absolute quantitative values (29). Using the IU as a standard for dosage, Bt must be applied regularly and in the correct quantity like a chemical insecticide. With formulation developments and other privately-funded improvements, a range of Bacillus formulations are available, with a large number of proprietary commercial products. Bt formulations typically have a low toxicity and, having long been compared with chemicals, have usually been assigned as Class III (moderate risk: caution) in the WHO/EPA toxicity classifications (30). In Southeast Asia, the majority of the Bt products are imported from the major agrochemical companies, but there are also local manufacturers. 2.1.2 Fungi According to the ABC database, entomopathogenic fungi (EPF) in the genera Metarhizium and Beauveria have been developed and used on a localised basis in a number of Southeast Asian countries for various pests including insects in the Hemiptera, Coleoptera and Diptera. The antagonistic fungi Trichoderma spp., including T. harzianum, has been used in several AMS for management of soil-borne diseases. Cases of successful biological control with fungi have been a driver for phylogenetic research on several important genera, using molecular techniques that frequently reveal a diversity that is remarkably greater than older classifications based only on morphological characteristics (e.g. the old 2 ‘varieties’ of Metarhizium anisopliae are now known to represent at least 9 different spp. (33). The species in Beauveria, Lecanicillium (five species that were previously ‘Verticillium lecanii’) and Trichoderma have likewise been revised.) Correct identification of fungal isolates is essential since we now understand that individual species may ‘target’ pests: often at the family level or more specifically. Inexperience with genetic characterisation and lack of technology are currently major obstacles in AMS to raise the quality of fungal BCA through proper identification and formulation. Future efforts to improve the situation should especially include the producers in the private sector. Improved characterisation of isolates or strains also will be beneficial to the regulators. Although pest management, based on fungi such as Beauveria and Metarhizium, has a century-long history of efficacy and safety, it must not be assumed that all fungal isolates are safe; for example, individual isolates in certain species of Trichoderma, Isaria (previously Paecillomyces) and even Metarhizium have been shown to produce secondary metabolites that may be risky to human health. Promising ‘new’ isolates and species must be identified accurately, and a toxicology profile prepared before advanced product development takes place. This was carried out for M. acridum, and products were developed for environmentally-sound locust and grasshopper control in the international LUBILOSA (34) Programme: which placed a range of ‘enabling technologies’ in the public domain for turning potentially beneficial fungi into useful, stable, practical products. 19
Implementing Biological Control Agents in the ASEAN Region
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