Pesticides, biological efficacy

Pesticide crystals can be coated by the process of coacervation [1]. Water-soluble polymers are used to suspend the crystals. The suspension is then manipulated to cause the polymers to insolubilize and harden to encapsulating shellwalls. While effective, these processes do not produce sub-micron particles. Usually matrix peirticles from thirty microns to fifty microns maximum dimension are obtained. Each matrix particle contains many of the primary particles. Full biological efficacy in foliar applications would be lost. 

The presence of micelles or microemulsions will have significant effects on the biological efficacy of an insoluble pesticide. In the first instance, surfactants will affect the rate of solution of the chemical. Below the c.m.c., surfactant adsorption can aid wetting of the particles and, consequently, increases the rate of dissolution of the particles or agglomerates [8]. Above the c.m.c., the rate of dissolution is affected as a result of solubilization. According to the Noyes-Whitney relation [122], the rate of dissolution is directly related to the surface area of the particles A and the saturation solubility, Cg, i.e. 

Owing to the prohibition of chemosynthetic pesticides under organic farming standards, there is a greatly reduced availability of intervention/treatment-based methods for disease and pest control in organic fruit production systems. The efficacy of the permitted biological control, extract or mineral element (e.g. S and Cu)-based crop protection products is also usually lower than of chemosynthetic pesticides. Permitted plant protection products show efficacies of between 60 and 80% while chemosynthetic fungicides and pesticides often have efficacy levels >95% (Tamm et al., 2004). 

Molecular genetic techniques now available hold great potential for improving strains for biological pesticide development. For example, low-virulence strains may be enhanced to improve efficacy. Species difficult to grow or that reproduce poorly in artificial culture may be genetically altered to make them available in large... 

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