Nano-Pesticides and Nano-Herbicides

Nanotechnology has potential for efficient delivery of chemical and biological pesticides using  nanosized preparations or nanomaterials based agrochemical formulations. The active ingredient is adsorbed, attached, encapsulated or entrapped unto or into the nano-matrix. Controlled release of the active ingredient is achieved due to the slow release characteristics of the nanomaterials, bonding of the ingredients to the material and the environmental conditions. The benefits of NMs based formulations are the improvement of efficacy due to higher surface area, higher solubility, higher mobility and lower toxicity due to elimination of organic solvents. Nanopesticides involve either very small particles of pesticidal active ingredients or other small engineered structure with useful pesticidal properties. Nanopesticides can increase the dispersion and wettability of agricultural formulations and unwanted pesticide movement. Nanomaterials and biocomposites exhibit useful properties such as stiffness, thermal stability, solubility, permeability, crystallity and biodegradability needed for formulating  nanopesticide.  Nanopesticides also offer large specific surface area and hence increased affinity to the target. Nanoemulsions, nanoencapsulates, nanocontainers and nanocages are some of the nanopesticides delivery techniques that have been discussed recently. Nanopesticides delivery techniques have the ability to control or delayed delivery, absorption and more effective and environmentally friendly approach. Currently spraying of pesticides involves wither knapsacks that deliver large droplets associated with splash loss or ultralight volume sprayer for controlled droplet application with smaller droplets causing spray drift. Constraints due to droplet size may be overcome by using NP encapsulated or nanosized pesticides that will contribute to efficient spraying and reduction of spray drift and splash losses. 

Basically, the nano-formulation should degrade faster in the soil and slowly in plants with residue level below the regulatory criteria in food stuff. The sodium dodecyl sulphate (SDS) is used to increase the photo-degradation of the nanoparticles in soil. The SDS modified Ag/TiO₂ imidacloprid nanoformulation has been developed using a microencapsulation technique that used chitosan and alginate. Formulation stability is also an important aspect at the nano level.  A stable nanopesticide (bifenthrin) using polymer stabilizer such as Polyvinylpyrrolidone (PVP), Polyvinyl alcohol (PVOH), and Poly(acrylic acid)-b-poly(butyacrylate (PAA-b-PBA) has been formulated successfully.

Plants provide a non-toxic source of molecules with proven biological efficacy that are usually non-persistent in fresh water and soil. However, phytochemcials such as secondary metabolites and essential oils face problems of stability and cost effectiveness. Incorporation of Artemisia arborescens essential oil into solid lipid NPs (200-204 nm) reduced the rapid evaporation of essential oil. Amorphous nanosilica is obtained from various sources such as the shell wall of phytoplankton, volcanic soil, displayed promising potential as a biopesticide. Nano-silica may be useful against stored grain, household pests, fungal organism, worms etc.

Bacteria, viruses and fungi can function as biological control agents against insect pests. Bacterial and viral formulations need to be ingested by the host and are susceptible to desiccation, heat and UV inactivation. The use of nano-formulations may offer new ways to enhance the stability of these biological agents. Mycopesticides or fungal biocontrol agents are promising as they act by contact and do not need ingestion, can be easily mess produced, and are relatively specific. Microbial products such as enzymes, inhibitor, antibiotics and toxins are promising as biopesticides against plant pests and pathogens. The insecticidal properties of bacterial toxins (Bt) are well known. However, microbial products need stabilization and directed delivery mechanism towards identified targets. Chitosan or clay as stabilizing and delivery agents have potential of biocompatible and biodegradable nanomaterials.

Unwanted plants along with the desired plant crops are called weeds. To kill these weeds, herbicides are used but conventional herbicide when sprayed has a chance of getting affected to the foods crops too by this and there can be huge loss in the crop yield. By using nano herbicide which is 1-100 nm range will try to mingle with the soil particle and try to destroy the entire weeds from their roots by not affecting other food crops. As the nanoparticles are target specific they can be used to kill the weeds and destroy it to get better yield. Herbicides like atrazine, triazine could be encapsulated to get efficient release to the plants.