Formulation improves the properties of active control agents (be they biological or chemical) for handling, storage, application and may substantially influence effectiveness and safety. However, regulatory authorities should be aware that with several microbial and even some modern chemical pesticides9, the mammalian toxicity of the formulating ingredients may exceed that of the active control agent. Formulation terminology follows an internationally recognised two-letter convention; unfortunately, many manufacturers still fail to follow these industry standards, which can cause confusion for users. Regulators should insist that all producers describe BCA with the easily recognisable formulation descriptors (and thus appropriate specifications) listed by CropLife (31) and FAO/WHO (32). The most frequently used products are formulations for mixing with water then applying as sprays, with older formulations such as wettable powders (WP) still in use. From the 1980s, conventional products such as emulsifiable concentrates (EC) were slowly replaced with formulations having reduced or no use of hazardous solvents and improved stability. Examples include suspension concentrates (SC) and water dispersible granules (WG) that are easier and safer to handle by the operator and have been used for microbial products such as Bt. In all cases, the formulation scientist seeks to minimise the rate of settling of particulate suspensions of microbials in the formulation bottle and sprayer tank, by minimising particle size. The rate of settling is governed by Stokes’ formula, whose most important factor is particle size: the only squared parameter in the equation. For microbials, particle size obviously cannot be less than that of a single propagule (colony forming unit), but there are likewise advantages in minimising constituents that do not exceed this size (to avoid nozzle blockage, etc.) As discussed in section 2.5.3, from a practical application point of view, one of the most important features of microbials is that they must be delivered to the target as particles: usually suspended in a liquid and dispersed as spray droplets. At a much more basic level, it is important that there are no large particles in the formulation which risk clogging filters and nozzles of spray equipment. The specific requirements for quality control of microbials will be heavily dependent on the 25 2.5 Formulations, quality control, and application techniques 2.5.1 Formulations of microbials nature of the organism and may be species-specific. Important specifications usually include: • Limits for contaminants (e.g. no human pathogens detected in 10,000 CFU sampled) • Viability at packing; viability profile over time (usually temperature dependent) … • ... for fungi, this affected by moisture content (see below) • Particle size specifications (formulation dependent: as above) 9 Microbials, plant extracts, fermentation products and relatively specific (non-neurotoxic) chemicals can be collectively termed ‘biorational pesticides’
Implementing Biological Control Agents in the ASEAN Region
To see the actual publication please follow the link above