Scientists develop sustainable insecticide using nanotechnology

A more effective and sustainable insecticide was developed by Embrapa Meio Ambiente (SP) in partnership with the Chemistry Institute of the State University of Campinas (Unicamp). The work resulted in a controlled release system for the insecticide molecule thiamethoxam. The encapsulation was carried out in polymeric nanomicelles, structures smaller than one billionth of a meter, or more than 80 thousand times smaller than the thickness of a strand of hair. Studies show that the application of nanopesticides can be much more effective compared to existing conventional pesticides and could, in the near future, completely replace them. Nanomaterials present unique physical, chemical and biological properties, different from the characteristics of the same materials on larger scales, due to the increase in the surface-to-volume ratio and quantum effects.

Nanopesticides refer to formulations that use nanomaterials in their composition and that have high application efficiency and less toxic effects on the environment compared to conventional formulations of the same active ingredient. In this work, the formulation method used was nanoencapsulation of the active ingredient studied, resulting in a sustained release by the nanoparticles, high stability and specificity. “The results indicated that the nanostructures were effective with a dose approximately twice lower compared to commercial formulations”, explains Embrapa analyst Marcia Assalin, coordinator of the study, which had support from the São Paulo State Research Support Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo (Foundation for Research Support of the State of São Paulo) ( Fapesp).

The efficiency of the nanoinsecticide was evaluated by controlling the insect in greenhouses (diaphorina citri) responsible for the spread of greening, also known as huanglongbing and HLB, caused by the bacteria Candidatus Liberibacter spp. The disease affects all citrus plants and has no cure: once contaminated, it is not possible to eliminate the bacteria from the plant, which acts as a source of inoculum for contamination of other plants.

In addition to increasing efficiency, the new product can lead to a reduction in the number of applications, attenuation in the development of pest resistance to the insecticide, and a reduction in environmental impact and associated costs.

According to Ljubica Tasic, a professor at Unicamp, the nanoinsecticide showed reduced toxicity to aquatic organisms used in ecotoxicity assessment studies (Raphidocelis subcapitata and Artemia salina). Therefore, she believes that the product obtained represents one of the ways in which nanotechnology can promote more sustainable agricultural practices. Agriculture, to be considered sustainable, must guarantee future generations the ability to meet the production and quality of life needs on the planet. To achieve this, it must be able to increase agricultural yield, using fewer resources, while reducing its environmental impact and ensuring the health of supporting ecosystems, in order to guarantee the continuity and quality of natural resources necessary for food production. .

Thiamethoxam and greening

Greening is one of the most important citrus diseases today. Its severity is mainly due to the rapid and efficient spread of bacteria by the insect. diaphorina citri and the absence of genetic resistance in citrus. Thiamethoxam, one of the active ingredients used to control the disease, belongs to a relatively new class of insecticides, neonicotinodes, which have been on the market since the early 1990s and are part of the list of best-selling pesticide products. This chemical product has high solubility in water, leaching potential and rapid degradation by photolysis, that is, the process of degradation of organic molecules using light.

Assalin states that, when applying conventional insecticides, numerous losses can occur due to several factors, such as application techniques used, environmental conditions, degradation by photolysis and leaching. This leads to repeated applications, resulting in the use of insecticides in quantities greater than necessary to control the insect vector. Thus, it causes a series of problems, such as increased treatment costs, contamination of surface and underground water bodies, risk of the psyllid developing resistance to the insecticide, in addition to posing a risk to human health and aquatic invertebrates. “Furthermore, it is extremely important to highlight that neonicotinoid insecticides are highly toxic to pollinating insects such as bees, having been banned from European Union fields for this reason,” he highlights.

Nanoencapsulated pesticide formulations allow controlled release of the active ingredient, as well as protection against premature degradation, enabling the use of conventional insecticides in a more efficient and sustainable way. Therefore, evaluating the effectiveness of encapsulated pesticide formulations is essential to enable their use in agriculture. Studies on the possible impacts on humans and the environment must be carried out, according to Assalin.

Writers

The article "Thiamehtoxam used as nanopesticide for the effective management of Diaphorina citri psyllid: an environmental-friendly formulation" (Thiamethoxam used as a nanopesticide for the effective management of the psyllid diaphorina citri: an ecologically correct formulation) was written by Marcia R. Assalin, Debora Cassoli de Souza, Maria Aparecida Rosa, Rafaela Duarte, Rodrigo Castanha and Elke Vilela, from Embrapa Meio Ambiente, Ljubica Tasic and Nelson Durán, from Unicamp.

Received the following summary:

Although insecticides are essential for the effective pest management, the development of sustainable formulations remains a challenge in modern agriculture. This work focuses on the encapsulation of thiamethoxam in polymeric micelles, a nanodelivery system. The nanomicelles, prepared by thin-film hydration method, presented 94.5 ± 10.26% of encapsulation efficiency, average size of 85.14 ± 2.23 nm, zeta potential of −5.3 mV, and acceptable homogenous distribution. Water solubility of thiamethoxam nanomicelles showed an increase by 41.7% in relation to thiamethoxam compound. Toxicity assessment was applied to Raphidocelis subcapitata Korshikov and brine shrimp Linnaeus organisms. The EC50 values ​​obtained for microalgae of polymeric nanomicelles > polymeric nanomicelles loaded thiamethoxam > commercial pesticide. EC50 values ​​obtained for brine shrimp in all treatments could not be compared due to lack of sensitivity shown by this organism to the adopted treatments. Nanoformulation effectiveness was evaluated against D. citri caged in citrus plants grown under greenhouse conditions, in comparison to that of standard formulations. Results have suggested that thiamethoxam nanomicelles might be effective in controlling D. citri around dose 2-fold lower than commercial formulations.

doi.org/10.1080/09670874.2022.2042425