Particulate Nanoinsecticides: A new concept in insect pest management

VALDEZ, S. R.; BUTELER, M.; GITTO, J. G.; STADLER, T.

Insecticides

InTech Open

Año: 2018; p. 83 - 105

Pest control using synthetic organic insecticides is facing economic and environmental challenges worldwide. The identification of new effective insecticidal compounds is crucial to provide viable alternatives to those conventional products, which lose efficacy to insecticide resistance and are potentially toxic and environmentally unfriendly. The current use of nanotechnology in a wide array of fields and products and the recent discovery of their potential in insect pest control, suggest that nanomaterials have a great potential for development of new products that will impact agriculture including insect pest control strategies. Nano-engineered alumina (NSA) has already been demonstrated to be effective against stored product insect pests, in laboratory bioassays. Its insecticidal activity of NSA is dependent on electric phenomena, both of the particles and of the target insects and on the specific surface area of the insecticide powder. Since NSA is synthesized by oxidation of metals, resulting particles show fixed electric charges. On the other hand, insects in general, exhibit their own electric charges generated by triboelectrification. We have found that negative electrostatic charged NSA particles adhere tightly to positive tribo-charged insect body surface. In contrast, diatomaceous earth (DE), a commercial microparticulate insecticide powder, shows a slight negative electrostatic charge, 8.13 times weaker than NSA. The mechanism of action of NSA involves two steps that occur in sequential order. First, a strong electrical binding between negatively charged NSA particles and the positive tribo-charged insect. Next, dehydration of the insect occurs due the strong sorbtive action of the NSA particles that remove the insect cuticular waxes responsible for insect cuticle waterproofing. Hence, the mechanism of action of NSA does target the water balance of the insect and dehydration is the leading cause of death. As postulated for insecticidal inert powders in general, insecticide particles attach to the insect cuticle surface producing a negative effect on insect water balance, but this effect decreases as ambient humidity increase. This decrease in efficacy of inert powders as ambient humidity increases can be explained by analyzing the effect of moisture on the interaction of the tribo-charged insect body surface and the electrically charged NSA particles where electrostatic bond forces are reduced by electrostatic discharge. So, hydrophilic substances as DE are more exposed to the influence of moisture than hydrophobic materials (NSA).The high insecticidal efficacy shown by NSA is a result of its intrinsic electric charge, small particle size and high sorptive potential due its large specific surface area. Thus, results show that NSA could provide an alternative to conventional synthetic organic insecticides due to its strong insecticidal properties and its mechanism of action which is different from conventional synthetic pesticides.