Nanomaterials in plant protection products

Pesticides or plant protection products are intended to protect plants from pests such as insects, microorganisms or vermin such as nematodes. The use of nanomaterials in this sector is based on a number of expected benefits, such as an increase in pesticide efficacy against pests which allows for the application of lower amounts of pesticides. However, such products are not currently on the market and are being researched extensively for their benefits and potential environmental risks.

What is a nanopesticide?

At present, there is no generally accepted definition of the term “nanopesticide” which is currently used differently in legislation, science, public and business.
One proposal is “A nanoparticide is a plant protection product that contains components in the nanometer size range (up to 1000 nm) and has new properties that are related to the small size of their components.” So, a size-based definition is not enough for nanopesticides, unlike other nanomaterials. Generally, pesticides always consist of several substances. Similar to a drug, the actual active ingredient is mixed with other accompanying compounds. Those allow the active ingredient to be easy to apply to the plant, to evenly distribute and to remain stable after use. In most of the proposed applications for nanopesticides, the nanomaterial itself is not the active agent, but acts as an auxillary compound to stabilize the active agent or enhance its controlled release (e.g. as a nanocapsule). Nano copper and nano silver are examples of nanomaterials as active agents.

Benefits of Nanopesticides

Often, the active ingredients in pesticides are poorly soluble in water, which makes their use difficult. Nanomaterials can increase the water solubility of the active ingredients as accompanying substances. In this way, the release and distribution can be better controlled and the active ingredient can be better protected against premature degradation. This not only improves the uptake and effectiveness of the pest control agent, it also significantly reduces the amount of pesticide used. Furthermore, alternative active ingredients and products are intended to be less harmful to the environment and possibly reduce the development of resistance of pests to pesticides. At present, however, there is little knowledge on the gain in effectiveness of nanopesticides compared to conventional pesticides.

Categories of nanopesticides

There are many types of nanopesticides. The nanomaterial is usually used as a carrier for the actual active ingredient in emulsions, capsules, gels, fibers and particles. Nanoparticles can also act alone as nanopesticides (e.g. copper).

Type	Relation to ´nano´	Benefits	Examples of active ingredients (target pests)
Nanoemulsions	The active ingredient is located in nanoscale oil droplets that float in an aqueous solution.	Improved distribution and increased uptake by organisms.	Neem oil (parasitic worms, insects) Permethrin (ticks, mosquitoes)
Nanocapsule	The active ingredient is packed in nanoscale capsules.	Increased uptake and thus increased effectiveness against pests.	Lansiumamide B (antibacterial, to treat tobacco bacterial wilt)
Nanogel	The active ingredient is distributed in a gel, which consists of nanoscale building blocks.	Easier handling, decreased evaporation of active ingredient.	Copper (antifungal activity) Essential oils (various pests)
Nanofibres	The active ingredient is incorporated in a nanoscaled fibre.	Improved distribution, slow release of active ingredient.	Thiametoxam (insecticide)
Liposomes	Liposomes are in nano sized particles.	Slow-release of active ingredient.	Etofenprox (insecticide) Pyrifluquinazon (insecticide)
Lipid nanoparticles	Nanoparticles composed of lipids that carry the active ingredient.	Slow release of the active ingredient, protection from degradation.	Deltamethrin (insecticide)
Inorganic nanoparticles	Inorganic nanoparticles as active ingredient.	Improved distribution, high effectiveness of active ingredient against pests.	Silicon dioxide Titanium dioxide Silver Copper Nanoclays
Inorganic nanoparticles associated with organic active ingredient	Inorganic nanoparticles act as carriers of organic active ingredient.	Enables slow release of the active ingredient.	Silicon dioxide Titanium dioxide

 

Risks of nanopesticides for the environment

Nanomaterials in nanopesticides are deliberately released into the environment due to the nature of their application. Therefore, benefits and risks to humans and the environment must be considered carefully. The EU Biocidal Products Regulation states that every manufacturer must prove that a pesticide is safe before admitting a product. Since 2013, nanomaterials have also been explicitly included in the regulation.
Despite the many ideas on how nanomaterials can be used to improve conventional pesticides, there are currently no nanopesticide products on the market. On the one hand, the development and approval of a pesticide is very tedious and expensive, on the other hand, it is currently unclear how great the savings by using a nanopesticide compared to a conventional pesticide really is.

The current understanding is not yet sufficient to reliably assess the benefits and risks of nanopesticides. Further studies on the fate and risks of nanopesticides in the environment are thus needed.

Nanopesticides are a novel class of plant protection products that promise a number of benefits to agriculture. However, both benefits and potential risks to the environment are still poorly understood. Research in this area is very active and will provide answers in the future on their applicability, risks and economic acceptance.

Literature

1. The Royal Society & The Royal Academy of Engineering; 2004. Nanoscience and nanotechnologies: opportunities and uncertainties. (PDF, 3.5 MB )
2. Gogos, A (2012), J. Agric Food Chem 60 (39): 9781-9792.
3. Kah, M et al. (2013), Crit Rev Env Sci Tec 43(16): 1823-1867..
4. Kah, M and Hofmann, T. (2014), Env Int 63:224-235.
5. Kah, M. (2015), Front Chem, 3(64): 64.
6. Regulation (EC) No 1107/2009 of the European Parliament and of the Council of 21 October 2009 concerning the placing of plant protection products on the market and repealing Council Directives 79/117/EEC and 91/414/EEC.
7. Amenta, V. et al. (2015), Regul Toxicol Pharmacol, 73(1): 463-476.
8. Kookana, Rai S. et al. (2014), J Agric Food Chem 62(19):4227-4240.
9. Kah, M. et al. (2018), Nature Nanotech.
10. European Chemicals Agency (ECHA) (EN) – Understanding BPR (last access date: July 2018)
11. European Chemicals Agency (ECHA) (EN) Biocidal Products Regulation: Legislation (last access date: July 2018)