Pesticide effects of highly stable green synthesized silver nanocomposites to be used in organic tomato crops.

Greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) together with the negative incidence of fungi such as Oidium neolycopersici and phytopathogenic bacteria, are responsible for causing serious economic losses in organic tomato crops. Silver nanoparticles (AgNPs) are a promising solution to problems caused by these pests due to their insecticidal and bactericidal properties. However, these compounds are unstable and tend to form agglomerates. This fact causes them to lose their properties so, preventing its use as an alternative to chemical pesticides in organic cultures. In this research, a novel one-step green synthesis method to obtain silver stable nanocomposites using rosemary extract (Rosmarinus officinalis L.) as green reducing agent was stablished. The polymer polyvinylpyrrolidone (PVP) was used additionally in the same synthesis reaction as AgNPs stabilizing agent. With this scalable one step synthesis, the obtained PVP-AgNPs nanocomposite showed particle sizes of 10.8 nm being highly stable during 326 days. At different assayed doses, this highly stable PVP-AgNPs nanocomposite, was able to control whitefly specimens efficiently with an average mortality rate of 98% after 10 days of the nanocomposite application to naturally infested tomato leaves grown under greenhouse conditions. Additionally, in a diffusion inhibition assay on agar plates, inhibition of Bacillus amyloliquefaciens, Pseudomonas syringae, and Xanthomonas sp growth was found. PVP-AgNPs nanocomposite was also effective to control Oidium neolycopersici in greenhouse grown tomato plants. To our knowledge, this is the first well-founded report related to a PVP-AgNPs nanocomposite obtained by green synthesis using rosemary extracts as reducing agent able to control whitefly and tomato powdery mildew, being a potential alternative to chemical pesticides in organic tomato crops.