Efficacy of encapsulated and non-encapsulated thyme essential oil (Thymus vulgaris L.) in the control of Sitophilus zeamais and its effects on the quality of corn grains throughout storage

Abstract

Maize is a cereal widely cultivated and consumed on the planet and, as an agricultural commodity, research strategies addressing productive bottlenecks are then highly appreciated. Among these, pest insects stand out for causing losses both in the field and in warehouses. Thus, thinking about the sustainability of the productive system, there is a need to develop more natural techniques for the management of insects, especially the application of essential oils. Among essential oils, thyme has proven bioactive potentials, however, its application is restricted due to its instability, and thus encapsulation may be a promising alternative for its preservation. In this context, the objective of this work was to evaluate the effect of the application of encapsulated and non-encapsulated thyme essential oil on the mortality and persistence of Sitophilus zeamais (Motschulsky, 1885) and on the quality parameters of corn grains throughout storage. Thyme essential oil was encapsulated by spray drying and evaluated for chemical composition and encapsulation efficiency. The effects of thyme essential oil application on the mortality and persistence of Sitophilus zeamais were evaluated for 150 days and on the quality of corn grains for 200 days. Insect mortality was dependent on concentration and exposure time, presenting the greatest effect for encapsulated thyme essential oil. Both oils, in all concentrations, showed repellent effect against S. zeamais, except for 1 h of exposure. The application of essential oils did not impact the water content, pH, leached solids, conductivity and staining of corn grains, however, treatments with application of encapsulated essential oil increased acidity and soluble solids content. The application of both thyme essential oils, encapsulated and non-encapsulated, were effective for the control of S. zeamais, without altering the quality characteristics of corn grains.