Nanostructured alumina against pulse seed insect pests. L’alumina nanostrutturata contro gli insetti dannosi alle sementi.

Insect pests constitute a major threat not only to stored grains and legumes for food but also to the seeds for sowing. Seeds, usually stored in relatively small quantities and in separate packages, are particularly susceptible to insect attack because of their long period of storage. Moreover, due to the global market, seeds insect infestation promotes the spread of invasive stored food pests. Numerous studies showed the effectiveness of nanoparticles against various arthropod species of economic importance. Due to their small size (1-100 nm), nanostructured materials, have been showed to have properties that are not shared by nonnanoscale particles with the same chemical composition. In this study, we evaluated the effectiveness of nanostructured alumina particles (NSA) against the main seed-infesting insect pests: Oryzaephilus surinamensis (Silvanidae), Stegobium paniceum (Anobiidae), and Tribolium confusum (Tenebrionidae). After sixteen days, the percentage of insect mortality at the highest NSA concentration tested (400 mg kg-1) was 100% for S. paniceum followed by O. surinamensis (80.64%) and T. confusum (79.41%). The median Lethal Concentration (LC50) values calculated by Probit analysis were 14.87, 61.53, and 127.17 mg Kg-1 for S. paniceum, O. surinamensis, and T. confusum, respectively. Besides, in vitro-tests indicated that nanoparticles have not affected seeds germination, sprout growth and root lengthening, and, by comparing the plants treated with no-treated plants, no differences were recorded in the leaf surface, stoma density and roots length. On the contrary, a positive effect of the NSA was observed on the shoot growth with the treated plants that were about 66% higher than the non-treated plants. Finally, using the EDX system coupled with the Scanning Electron Microscope (SEM), no contamination by alumina nanoparticles was found on the surface of the P. vulgaris leaves of plants originated from the treated seed. The efficacy of NSA against the insect pests, and the absence of negative effects on seed germination and plant growth, indicate that NSA could represent a viable alternative to synthetic insecticides, for the seeds coating.