Growth and development of Tribolium castaneum (Herbst) on rice flour and brown rice as affected by time and temperature

Authors: Arthur, Franklin; STARKUS, LAURA - Arkansas State University; Gerken, Alison; Campbell, James - Jim; MCKAY, TANJA - Arkansas State University

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2019
Publication Date: 8/15/2019
Citation: Arthur, F.H., Starkus, L.A., Gerken, A.R., Campbell, J.F., McKay, T. 2019. Growth and development of Tribolium castaneum (Herbst) on rice flour and brown rice as affected by time and temperature. Journal of Stored Products Research. 83:73-77. https://doi.org/10.1016/j.jspr.2019.04.005.
DOI: https://doi.org/10.1016/j.jspr.2019.04.005

Interpretive Summary: The red flour beetle is a common pest in rice milling facilities, and can also feed on a range of rice fractions and by-products, including brown rice and rice flour. Development of red flour beetles is impacted by both diet and temperature, so variation in the type of rice fraction and temperature that can be found in rice mills might impact the ability of populations to increase. We evaluated red flour beetle development on brown rice and rice flour at 70, 80, or 90°F over a period of time from 2 to 10 months and found that reducing temperatures to 70°F, prevented increases in number of adults on both brown rice and rice flour, which are both optimal diets found in rice mills. At the two warmer temperatures, adult numbers increased rapidly before leveling off on both brown rice and rice flour, but number of larvae and pupae in the population tended to remain low. The low number of immature stages and stabilized population size may be the result of cannibalism by adults. Predictive modeling studies also showed little population increase beyond 10 months at 80 and 90°F, but although not measured in this study given enough time populations should decrease as food becomes limited. Reducing temperature in milling facilities where packaged brown rice and rice flour are held could be a viable strategy for limiting product damage caused by the red flour beetle.

Technical Abstract: Tribolium castaneum (Herbst), the red flour beetle, is a cosmopolitan stored product insect that can feed on a variety of raw grains and processed grain products. Although developmental studies have been conducted in the past there are no recent studies that examine the concept of population growth and development on a fixed resource. In this study, ten mixed-sex adults were exposed on 200 g of either rice flour or brown rice, and populations were assessed after 2, 4, 6, 8, and 10 months at 22, 27, or 32°C. At 22°C, the number of adults, pupae and larvae on rice flour and brown rice remained low throughout the 12-month storage period. At 27°C, the number of adults on rice flour increased to a maximum at 8 months, while adult populations on brown rice remained relatively constant from 2 to 10 months, with few pupae or larvae in the samples. At 32°C, adult populations on rice flour and brown rice were constant after month 2, with low numbers of pupae and larvae. Adult predation could have accounted for low numbers of pupae and larvae. Using the original 10-month data, populations were projected an additional 14 months to estimate if population patterns would remain similar over time. Adult numbers showed a steady increase over time at all temperatures on rice flour and brown rice at 22°C but numbers seemed to stabilize at 27 and 32°C. For both diets at 27 and 32°C, projected pupae and larvae numbers remained steady but low compared to adults. However, populations would not be expected to increase indefinitely because at some point the resources would become limited and populations would crash or decline. Results suggest that T. castaneum can rapidly deplete fixed resources such as bags of rice flour or brown rice when temperatures equal or exceed 27°C. Reducing storage temperatures to even 22°C may be a viable approach to mitigating population growth and dispersal of T. castaneum in bagged and processed grain products.