Elimination of the Common Bean Weevil Acanthoscelides obtectus (Say) by Hermetic Storage of Dry Common Bean at Different Moisture Contents

Abstract

The objective of this research was to determine the required storage time as well as the dry common bean (Phaseolus vulgaris L., Fabaceae) moisture content, to favor oxygen depletion and carbon dioxide increment for elimination of all stadia of the common bean weevil Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae). Experimental units with 150 g of dry bean (with moisture content around 10, 12, and 16%) infested with 20 adult insects were stored 21 d under hermetic and non-hermetic conditions. Oxygen/carbon dioxide levels, moisture content, insect mortality of initial infestation, emergence of the insects from the first generation (F1) and percentage of damaged dry bean were registered. In non-hermetic storage, the dry bean presented up to 395 insects from F1; and with damage up to 51.1%. Oxygen and carbon dioxide levels which did not allow the development (F1 emergence) of A. obtectus and the subsequent damage to the dry bean were between 0.5 - 3.5% and 8.9 - 9.7%, respectively. Hermetic storage system after 6, 9 and 12 d did not showed damage for moisture contents of 10, 12 and 16% respectively. With low moisture contents of the grain, there is lower consumption of oxygen and less carbon dioxide production by adult insects. On the contrary, with high grain moisture content insect activity increases with more consumption of oxygen and more carbon dioxide in less time, these results showed that high carbon dioxide and low oxygen levels joined with low grain moisture inhibit insect development in less time under hermetic storage.