Influence of various temperatures on the saw-toothed grain beetle Oryzaephilus surinamensis L. (Coleoptera: Silvanidae) and the potential use for management in stored dates

Abstract

The saw-toothed grain beetle Oryzaephilus surinamensis L. has emerged as a key pest of stored loose dates. This investigation aims to elucidate the effects of various temperatures on the beetle. About 52% of tested adult beetles survived without food for 10 days at temperatures of 4 °C and 18 °C, whereas at 0 °C, only 7% survived for 8 days, and at 27 °C, 12% survived for 10 days. Moreover, three stages of the beetle were incubated at −20 °C for different durations. They were kept either free or inside dates during the treatment. The mortality rate of free adult beetles at −20 °C was 2%, 61%, and 86% in 15 min, 20 min, and 25 min, respectively. Thirty-minute exposure at −20 °C resulted in 100% mortality of the treated adults. However, when the beetles were protected inside date fruits, the mortality rate was only 25% after 1 h of incubation at −20 °C. Alternatively, 2 h of exposure at −20 °C caused 100% mortality of the beetles despite being protected inside the dates. Similarly, treatment of larvae without food at −20 °C resulted in a mortality of about 93% of the populations in 30 min, but when the larvae were protected inside dates, 100% mortality occurred within 2 h. Furthermore, 2 h of exposure at −20 °C inhibited the hatchability of eggs inside dates by about 96.7%. These results could provide a valuable alternative to fumigation and other pesticides for the management of O. surinamensis in stored dates.