Particulate Nanoinsecticides: A new concept in insect pest management

STADLER, T.; BUTELER M.; RUTH VALDEZ SUSANA; GITTO JAVIER G.

Insecticides

INTECH

Año: 2018;

The current use of nanotechnology in a wide array of fields and products as well as the recent discovery of their potential in crop protection suggests Pest control using synthetic organicinsecticides is facing economic and environmental challenges worldwide. The identification of new effective insecticidal compounds is crucial to deal with the insecticide resistance to provideviable alternatives to conventional products. 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 as well as in insect pest control strategies.For example, nanoengineered alumina (NSA) is the result of combustion synthesis, using a redox mixture, with glycine as fuel and aluminum nitrate as oxidizer, where the final product is a homogeneous powder of high purity with uniform characteristics and specific physicochemical properties. This dust has already been demonstrated to be effective against stored product insect pests, in laboratorybioassays. In our recent studies on NSA we demonstrated that its insecticidal activity is dependent on electric phenomena, both of the particles and of the target insects and on the surface activity of the nanoinsecticide.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 thatnegative electrostatic chargedNSAparticles adhere tightly to positive tribo-charged insectbody surface. In contrast,diatomaceous earth (DE), a commercial microparticulate dust used against stored product insects,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 removing the insect cuticular waxes responsible for insect watertight. 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 can be explained in sorbtive insecticide powders as NSA by analyzing the effect of moisture on the interaction of tribo-charged insect body surface and the electrically charged NSA particleswhereelectrostatic bond forces were reduced by electrostatic discharge. So, abrasive and hydrophilic substances as DE are more exposed to the influence of moisture than hydrophobic materials (NSA). DE has a similar mode of action as NSA but NSA is more effective given its nanoparticulate size, greater sorptive potential and electric charge. Thus, results show that NSA could provide an alternative to conventional synthetic organic insecticidesdue to its strong insecticidal properties andits unique mechanism of action which is different from conventional synthetic pesticides.