Deep-freezing as a novel disinfestation strategy to rice weevil (Sitophilus oryzae Linnaeus) in packaged milled rice grains: Factors and lethal behaviors

Abstract

Rice weevil (Sitophilus oryzae Linnaeus) is a major insect pest of milled rice grains, which poses a great threat to food security. In this study, the feasibility of three deep-freezing regimes (-20, -80, and -196 oC) to disinfest packaged milled rice grains was explored. It was found that the disinfestation efficiency increased with the decrease in freezing temperature. For naked insects, complete mortality was achieved by the regimes at -20, -80, and -196 oC with the exposure time of 8 min, 2 min, and as short as 1 s, respectively. For insects in packaged rice grains (5 insects/500 g rice; package size: 8 cm × 5 cm × 13 cm), the corresponding exposure time was determined as 100, 40, and 4 min, respectively. Upon the increase in insect population density and package size, the longer exposure time was required for complete mortality. When the regime at -196 oC (1.5 min) was used as a pretreatment at -20 oC (60 min), the highest combination index (2.12) was obtained for the complete mortality. In one word, deep-freezing was successfully developed as a novel method to disinfest adult rice weevil in packaged milled rice grains.