Crop protection is an important part of agricultural activities. Further development in crop protection methods is required to meet increasing food production demand and overcoming the negative effects of climate change. 

Nanotechnology offers promising solutions to these problems through the development of effective and selective nanopesticides.

Introduction

The combined effect of increasing human population and climate change has raised concerns about food production and supply. The Food and Agricultural Organization of the United Nations (FAO) has published a report that supports the concerns on world food production. According to this report, the predicted 9.1 billion world population by 2050 will require a 70% rise in food production. Such an increase in food production faces several challenges such as energy prices, urbanization, drought, a decrease in soil quality, etc. Additionally, production yields should be improved to achieve sufficient food production. One of the important strategies to obtain high crop yield is improving crop protection methods. Crop protection is a wide area of practice that includes tools, products, and practices farmers use to defend their crops against weeds, disease, and harmful insects and fungi. Each year, these undesired conditions cause substantial loss of production and decrease crop yield. Several different systems and products are used to avoid these damages. However, innovative solutions and improved efficiencies are required to obtain better results in crop protection. For this purpose, scientists have recently been resorting to nanotechnology. The desirable characteristics of nanotechnology are utilized to improve herbicides, fungicides, bactericides, and insecticides on weed and phytopathogens. The advantages of nanosized systems include enhanced bioavailability, targeted delivery, controlled release, protection against degradation, and higher potency.

What is the Role of Nanotechnology in Crop Production?

Nanotechnology is used to develop effective nanopesticides including nanoherbicides, nanofungicides, nanobactericides, and nanoinsecticides. Modern agriculture resorts to nanoherbicides for effective inhibition of unwanted vegetation. Nanosized formulations of current herbicides and new nanoherbicides formulations both focus on the effective delivery of the material and selective application. The potential selectivity of nanoherbicides can provide inhibition of specific weeds without damaging valuable vegetation. This approach provides safer herbicides for both the human race and the environment. Different metallic active ingredients and polymeric nano systems are used for the development of nanoherbicides.

A considerable portion of diverse fungi species can cause harm to plants and result in decreased crop yields. Although it is not limited to this list and contains over 250,000 fungi species, some of the well-known harmful fungi species for food production can be listed as Botrytis, Sclerotinia, Aspergillus, Fusarium, and Verticillium. Hence, developing nanofungicides that target specific fungus species is important for crop protection. Similarly, over 15,000 species of bacteria are considered to be harmful to plants and cause production losses worldwide. Harmful bacteria species include Erwinia, Acidovorax, Pseudomonas, Ralstonia, Rhizobacter, Xanthomonas, Agrobacterium, Xylella, Arthrobacter, Clavibacter, and Streptomyces. Nanobactericides that target hazardous bacteria can help to obtain better crop protection. Both inorganic and inorganic nanomaterials and nano systems are utilized for the development of nanobactericides and nanofungicides.

Insects are another type of notorious problem in agriculture. Almost every plant is vulnerable to different types of insects that destroy the crop, infest the product, and cause a serious decrease in production yield. Hence, insecticides hold an important place in agriculture. Incorporating nanotechnological solutions to insecticides can provide an effective and selective process as well as environmental protection. Organic or inorganic nanopesticides can be applied against insect eggs, larvae, or adult insects.

Nano Systems and Nanomaterials for Crop Protection

Nanotechnology is used for the encapsulation of nanopesticides or to develop active nanomaterials. Polymer based nano systems can be utilized as encapsulating materials while nanosized nanomaterials are utilized as active ingredients in nanopesticides. Encapsulating nano systems can consist of both synthetic and organic polymers. The most common polymer nano systems for crop protection are nanocapsules, nanospheres, nanogels, and micelles. The solid or liquid core of nanocapsules consists of active nanopesticides particles while a polymeric shell encapsulates and forms the outer layer. Nanocapsules are produced through different methods the active ingredients are then loaded into the polymeric capsule. Nanospheres are similar structures to nanocapsules; however, the material polymerizes along with the active ingredient and captures nanopesticides during formation. Micelles are specifically used to deliver water insoluble nanopesticides. For this purpose, amphiphilic block copolymers are utilized. The hydrophilic copolymer faces outwards while the hydrophobic copolymer faces inwards encapsulating the nanopesticides material. Nanogels are formed through the cross linking of hydrophilic polymers. These structures can swallow and take up a considerable amount of nanopesticide materials providing an effective delivery method.

Similar to polymeric materials, lipid-based structures such as nanoliposomes and solid lipid nanoparticles are also utilized for the effective delivery of nanopesticides. Active materials can be trapped in these structures. Nanoliposomes are made up of a lipid bilayer shell and an aqueous core containing active ingredients while solid lipid nanoparticles capture nanopesticides through recrystallization. Porous nanoparticles such as silica nanoparticles and nanoclays also provide a suitable environment for nanopesticide loading. These nanoparticles are advantageous due to their environment friendly nature and abundance. Functionalized porous silica nanoparticles can be absorbed in the insect cuticular membrane lipids, damaging their protective waxy layer and causing dehydration. Furthermore, the porous nature of silica and clay nanoparticles allows the slow and controlled release of active ingredients.

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Metallic, nonmetallic nanoparticles and their composites can be utilized as active nanopesticide materials. These nanoparticles show unique physical, chemical, optical, and biological properties along with improved activity due to their high surface area. The most common metallic nanoparticles in crop protection are silver, silver oxide, gold, zinc oxide (ZnO), titanium oxide, magnesium oxide, and copper oxide. Silver nanoparticles are effective against bacteria and spore-forming fungi; however, they are nontoxic to animals which make them promising candidates as nanopesticides. ZnO nanoparticles act as nanobactericides due to their phototoxicity and electrostatic interaction with the bacterial cell surface. Another well-known nanoparticle for its antibacterial property is TiO₂. Titanium dioxide nanoparticles are effective nanobactericides since they cause site-specific damage in DNA and proteins of the pathogen. Similarly, Cu nanoparticles, MgO nanoparticles, and Silica nanoparticles show antibacterial properties and are used as nanobactericides materials. Apart from metallic NPs, other materials such as silica-based, C-based, sulfur-based, and aluminum-based NPs are also used in crop protection. In addition to utilizing nanosystems and nanoparticles separately in crop protection, the composite structures of these materials are also utilized as nanopesticides. Ceramic matrix composites, metal matrix composites, and polymer matrix composites can provide brilliant effective nanopesticide systems. Carbon nanotubes are found to be excellent carriers and active materials in nanopesticides.

All of these nano scale solutions are currently being investigated and utilized in enhanced agricultural applications for crop production in the hopes of improving production yields.

Conclusion

The rapid growth of the human population has increased the demand for agricultural production. Meanwhile, agriculture has been under the detrimental effect of climate change, urbanization, and decreased soil quality. This is why novel approaches for improving food production is necessary to meet increasing demands. Crop protection holds an important place in achieving this goal. Crop protection battles with weeds, disease, and harmful insects and fungi which decrease plant yields significantly. Current crop protection methods are found to be ineffective and wasteful. Hence, scientists have turned to nanotechnology to develop effective crop protection mechanisms. These studies have led to the development of nanoherbicides, nanofungicides, nanobactericides, and nanoinsecticides.

Nanotechnology utilizes nano systems for the effective delivery of nanopesticides or nanomaterials as the active ingredients in nanopesticides. Nano delivery systems can be based on polymeric or lipid nanostructures. The most common polymer nano systems for crop protection include nanocapsules, nanospheres, nanogels, and micelles while lipid nanostructures for crop protection include nanoliposomes and solid lipid nanoparticles. These structures encapsulate active ingredients and provide selective release of nanopesticides. Porous silica and clay nanoparticles are also suggested as nano carriers for nanopesticides. Nanomaterials that are used as active ingredients in nanopesticides can be metallic, non-metallic nanoparticles, or composite nano systems. Metallic nanoparticles utilized in crop protection methods include silver, silver oxide, gold, zinc oxide (ZnO), titanium oxide, magnesium oxide, and copper oxide. Non-metallic nanoparticles such as silica-based, C-based, sulfur-based, and aluminum-based nanoparticles are also reported as effective nanopesticides. Crop protection methods based on nanotechnology can either use these delivery systems and active nanoparticles separately or as a composite system. Regardless, scientists are able to develop effective and selective crop protection systems by utilizing these nanotechnological solutions. It is important to note that crop protection is still open to further improvement.

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References

1.Ojha, S., Singh, D., Sett, A., Chetia, H., Kabiraj, D., & Bora, U. (2018). Nanotechnology in crop protection. In Nanomaterials in Plants, Algae, and Microorganisms (pp. 345-391). Academic Press.

2.Shang, Y., Hasan, M., Ahammed, G. J., Li, M., Yin, H., & Zhou, J. (2019). Applications of nanotechnology in plant growth and crop protection: a review. Molecules, 24(14), 2558.

3.Jampílek, J., & Kráľová, K. (2018). Benefits and potential risks of nanotechnology applications in crop protection. In Nanobiotechnology Applications in Plant Protection (pp. 189-246). Springer, Cham.

4.Crop Protection. (n.d.). Retrieved October 28, 2020, from https://www.bayer.com/en/crop-science/crop-scienc...