Development and immature mortality of the saw-toothed grain beetle, Oryzaephilus surinamensis, on different sorghum fractions

Authors: LAMPIRI, EVAGELIA - University Of Thessaly; Scully, Erin; ARTHUR, FRANKLIN - Retired ARS Employee; ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2022
Publication Date: 3/1/2023
Citation: Lampiri, E., Scully, E.D., Arthur, F.H., Athanassiou, C.G. 2023. Development and immature mortality of the saw-toothed grain beetle, Oryzaephilus surinamensis, on different sorghum fractions. Journal of Economic Entomology. 116(2):615-620. https://doi.org/10.1093/jee/toad024.
DOI: https://doi.org/10.1093/jee/toad024

Interpretive Summary: The sawtoothed grain beetle (Oryzaephilus surinamensis) is a high profile cosmopolitan insect pest of high value processed food products and raw grains. Characterized by its high mobility, its short development time, and its ability to feed on multiple commodities, these insects can cause significant economic losses to a variety of commodities including grains, oilseeds, nuts, and fruit. Sorghum production and milling has rapidly increased in the central plains region of the United States over the past decade because of its adaptability to arid climates and a high consumer demand for products containing gluten-free flour. Its susceptibility to damage and infestation by stored product insects is not well characterized and the goals of this study were to determine if various products generated during milling were susceptible infestations (Bran, Shorts, Coarse grits, Fine grits, Red dogs and Flour). Although insect development was slower on flour, all fractions readily supported development from egg to adult. This finding suggests that sorghum milling facilities could support populations of sawtoothed grain beetle and that concerted efforts should be made to monitor for insect activity and clean up small spillage piles that could harbor insect infestations.

Technical Abstract: Development ability of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) was examined on six different sorghum milling fractions: Bran, Shorts, Coarse grits, Fine grits, Red dogs and Flour, and also on a standard diet of Oat Flakes. For this purpose, a 1-day-old egg was placed in a vial containing a1 g of one of the sorghum fractions or on the oat flakes, and held at each fraction and exposed to three different temperatures, 25, 30, or 32°C. After two week, all vials were checked daily for pupal and adult emergence and also mortality of immatures. The developmental time of O. surinamensis was significantly affected by the type of sorghum fraction. At all temperatures examined, the longest developmental times for both pupation and adult emergence were observed in Sorghum flour and Oat flakes compared to the rest of the sorghum milling fractions. Increasing the temperature from 25 to 30 and 32°C accelerated the development of this species, while adult emergence time did not differ significantly between 30 and 32 °C for all sorghum milling fractions except Sorghum flour. Immature mortality was greatest during the egg stage for the majority of the sorghum fractions and different temperatures tested. However, the lowest overall immature mortality occurred at 30 °C compared to 25 and 32 °C for 5 out of 7 sorghum fractions. The findings of the present work show that O. surinamensis can develop and survive in sorghum milling fractions and that the optimal temperatures for the growth enhancement are 30 and 32 °C. Results show that temperatures within sorghum milling facilities could support O. surinamensis development on milling fractions if they are not addressed through phytosanitary measures.