Production and efficacy of neem nanoemulsion in the control of Aspergillus flavus and Penicillium citrinum in soybean seeds

Abstract

The search for alternative methods that are efficient to control phytopathogens is extremely important. For this purpose, the aim of this study is to develop and characterize Neem oil nanoemulsions (Azadirachta indica), as well as evaluate its applicability to fungi Aspergillus flavus and Penicillium citrinum in soybean seeds. Soybean seeds were placed with nanoemulsion containing different Neem oil concentrations (0.5%, 1%, 2%, and 3% w/v) for t1 (600 min) and t2 (30 min). Control samples (positive: infested and untreated; and negative: not infested and treated) were also carried out. Prior to the treatments, the formulated nanoemulsions were characterized by dynamic light dispersion, polydispersity, rheology, and stability test. Subsequently, the soybean seeds were treated with nanoemulsion and then tested for germination and health. The nanoemulsion showed a mean droplet diameter of 59 ± 0.6 nm, and a viscosity of 2.542 ± 0.07 mPa s. The droplet sizes in the nanoemulsion were stable for a period of 20 days and the polydispersity remained around 0.209 ± 0.02. Neem oil had an inhibitory effect on the growth of fungal isolates, being that the highest antifungal activity was observed at the concentration of 3% (w/v) (28 mm inhibition zone for A. flavus and 25 mm for P. citrinum). Neem oil nanoemulsions were efficient against the studied fungi and did not present phytotoxic effects to the seeds. Nanoemulsion is easily accessible, economically viable and, in addition, less toxic than common synthetic pesticides. This study showed that Neem oil nanoemulsions have significant potential applications in agriculture.