Development of Rhyzopertha dominica (Coleoptera: Bostrychidae) on sorghum: quality characteristics and varietal susceptibility

Authors: Arthur, Franklin; Bean, Scott; Smolensky, Dmitriy; Cox, Sarah; Lin, Haijing; PEIRIS, SHANTHA - Kansas State University; PETERSEN, JAYMI - Kansas State University

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2020
Publication Date: 3/9/2020
Citation: Arthur, F.H., Bean, S.R., Smolensky, D., Cox, S.R., Lin, H., Peiris, S., Petersen, J. 2020. Development of Rhyzopertha dominica (Coleoptera: Bostrychidae) on sorghum: quality characteristics and varietal susceptibility. Journal of Stored Products Research. https://doi.org/10.1016/j.jspr.2020.101569.
DOI: https://doi.org/10.1016/j.jspr.2020.101569

Interpretive Summary: Different varieties of grains will show varying levels of susceptibility to stored product insects, including the lesser grain borer, a primary internal pest of stored grains. However, there have been few studies that evaluate susceptibility of sorghum varieties grown in Kansas to this insect pest. We conducted studies by exposing adult lesser grain borer on four different sorghum varieties, a while sorghum, a red-waxy starch sorghum, a red tannin sorghum, and a non-tannin red sorghum. We assessed progeny production and insect damage, along with physical and chemical attributes of the sorghum varieties. Progeny production was generally lower on the waxy red sorghum, and was often higher on the red-tannin variety sorghum. Starch content and kernel hardness was lowered in the red-tannin sorghum as well, and could be correlated with the insect development. Total phenolic content was much greater in the red-tannin variety compared to the others, but this high phenolic content did not seem to affect insect development. Indications were that the insects by-passed the bran layer where the tannins were concentrated and fed on the germ and endosperm. Results indicate further study is needed to more precisely relate kernel characteristics to susceptibility to internally-feeding stored product insects, but this study provides data that managers of storage facilities could use to potentially limit insect damage by segregating susceptible sorghum varieties during storage.

Technical Abstract: A white low polyphenol sorghum, a red-waxy starch sorghum, a red-tannin sorghum with moderate polyphenol levels, and a red non-tannin red sorghum were evaluated for susceptibility to Rhyzopertha dominica (F), the lesser grain borer. Density levels of 0 (untreated controls), 10, 20, or 30 mixed-sex adults were exposed on 100 g replicates of each of the varieties and removed after two weeks. Progeny production and physical damage were evaluated on each variety, along with quality characteristics such as moisture content, protein, starch, and phenolic content, and kernel vitreosity. Progeny production and physical damage varied with density level and variety, but was generally lowest on the waxy red sorghum. At the density level of 30 parental adults more progeny was found in the red-tannin sorghum compared to the other varieties. Starch content, kernel vitreosity and hardness was lower in the red-tannin sorghum. Total phenolic content was 2-3x greater in the red-tannin sorghum compared to the other varieties, but the high phenolic content did not seem to affect R. dominica progeny production. Results suggest the insects by-passed the bran layer of the sorghum varieties to feed on the germ and endosperm. Results of this study could be used to further explore the relationships between kernel hardness, chemical composition, and susceptibility to stored product insects, and incorporate results into management programs for maintaining quality of stored sorghum and processed sorghum food by-products and food additives.