Feeding substrate and temperature interplay determining infestations and losses by the sawtoothed grain beetle (Oryzaephilussurinamensis)

Abstract

Sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), is a secondary pest of stored products and one of the serious insect pests of cereal grains, commodities and packaged food throughout the world. However, this species is a concern beyond cereal grains, what may be differentially affected by temperature. Therefore, insect developmental time, larva and pupa survival, and adult emergence of O. surinamensis were assessed on different substrates (rice, sesame and date palm) at different temperatures (20, 25, 30 and 35 °C and 65% r.h). The substrate loss incurred by this insect infestation was also recorded. The larval stage was the main determinant for the overall developmental time of the sawtoothed grain beetle, regardless of the substrate and temperature tested. Adult emergence was affected by substrate (F2,48 = 4.50, P = 0.02) and particularly temperature (F3,48 = 24.94, P < 0.001), but not their interaction (F6,48 = 0.40, P = 0.87), exhibiting little variation until reaching 30 °C, but with a quick decline at 35 °C. The performance of the insects in rice was better, and worse in dry date. Furthermore, the survival was inversely related to substrate loss, regardless of the substrate used for rearing the sawtoothed grain beetle. Thus, substrate and temperature range are major determinants of sawtoothed grain beetle infestation with consequences for this species management.