Lethal time at different temperatures and date variety preference of the saw-toothed grain beetle in stored dates

Abstract

This electronic document is a “live” template. The various The saw-toothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), is the most important insect pest attacking stored dates in the United Arab Emirates. We sought to determine the time required to cause 100% mortality (lethal time) in O. surinamensis adults incubated at different temperatures, to measure temperature penetration time inside a date mass, and to study date variety preference of O. surinamensis adults. To do this, adults of O. surinamensis were separately incubated at -22℃, 50℃, and 55℃, for 5, 10, 20, 30, 60, 90, and 120 min, per temperature treatment; and we used feeding choice tests on four date varieties (Khelas, Fardh, Lulu, and BuMaán). Results showed that the lethal times of O. surinamensis adults, incubated at -22℃, 50℃, and 55℃, without dates, were 5, 10, and 20 min, respectively; while they were several times higher (30, 90, and 120 min, respectively) in the presence of dates. Results also showed that bigger date masses required either more heating or more freezing time to reach lethal temperatures. We found Khelas to be the least preferred date variety. Future studies should evaluate if heat and chilling injury affect postharvest date quality.