Development and Immature Mortality of the Sawtoothed Grain Beetle (Coleoptera: Silvanidae), on Different Sorghum Fractions and Different Temperatures.

Abstract

Developmental ability of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) was examined on six different sorghum milling fractions: Bran, Shorts, Cgrits, Fgrits, Red dogs, Flour, and also on a standard diet of Oat Flakes. For this purpose, a 1-day-old egg was placed in a vial containing 1 g of one of the sorghum fractions and exposed to three temperatures: 25, 30, or 32°C. All vials were checked daily for pupal and adult emergence and mortality of immatures. The developmental time was significantly affected by the type of sorghum fraction. After two weeks, for most of the temperatures examined, the longest developmental times in most cases for both pupation and adult emergence were observed in Flour and Oat flakes. Increasing the temperature from 25 to 30 accelerated the development, while adult emergence time did not differ between 30 and 32°C for all fractions except Flour. Egg mortality ranged from 11 to 78%, while larval and pupal mortality ranged from 0 to 22 and 0 to 45%, respectively for all sorghum fractions and different temperatures tested. Moreover, the mean overall immature mortality occurred at 30°C was 49.2, 39.7, and 65.1% at 25, 30, and 32°C for all the diets examined. The findings of the present work show that O. surinamensis can develop and survive in sorghum milling fractions and that the optimal temperatures for growth enhancement are 30 and 32°C. The temperatures within sorghum milling facilities could support O. surinamensis development on milling fractions if they are not addressed through phytosanitary measures.