Effects of sulfur dioxide fumigation on mortality of confused flour beetle (Coleoptera: Tenebrionidae) and rice weevil (Coleoptera: Curculionidae)

Authors: Liu, Yong Biao

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2024
Publication Date: 7/10/2024
Citation: Liu, Y.-B. 2024. Effects of sulfur dioxide fumigation on mortality of confused flour beetle (Coleoptera: Tenebrionidae) and rice weevil (Coleoptera: Curculionidae). Journal of Economic Entomology. https://doi.org/10.1093/jee/toae156.
DOI: https://doi.org/10.1093/jee/toae156

Interpretive Summary: There is a lack of effective alternative fumigants to replace methyl bromide for stored product insect control. The two current alternatives, phosphine and sulfuryl fluoride have their shortcomings and could not meet the need of postharvest pest control. Sulfur dioxide (SO2) has a long history to be used as a pesticide. However, it has not been used to control stored product insects. In this study, SO2 fumigation was evaluated for controlling confused flour beetle and rice weevil, two major stored product insects. Three-hour fumigations with 0.1 to 2% SO2 were conducted against all life stages of the two insects. Effective control of both species was achieved. However, there were considerable differences between the two species and among different life stages in susceptibility to SO2 fumigation. Confused flour beetle was more susceptible to SO2 fumigation than rice weevil. For confused flour beetle, complete controls of adults and all immature life stages were achieved in 3-h fumigations with 0.5 and 2% SO2 respectively. For rice weevil, 3-h fumigations with 2% SO2 resulted in 99.27% adult mortality and 87.5% mortality of immature life stages. This is the first study showing effective control of confused flour beetle and rice weevil with SO2 fumigation. Because SO2 is a GRAS (Generally Recognized As Safe) compound, SO2 has potential to be a safer alternative than most other fumigants for postharvest pest control on stored products.

Technical Abstract: Sulfur dioxide (SO2) fumigation was studied in laboratory to determine its potential as an alternative treatment for postharvest control of stored product insects confused flour beetle, Tribolium confusum, and rice weevil, Sitophilus oryzae. Three-hour fumigations with 0.1-2.0% SO2 were conducted against eggs, immature stages, and adults of the two insects at 20'C. Effective control of both insects was achieved. However, there were considerable variations between the two insects and among different life stages. Confused flour beetle was more susceptible to SO2 fumigation than rice weevil. Complete controls of adults and all life stages of confused flour beetle were achieved in 3-h fumigations with 0.5 and 2.0 % SO2 respectively. For rice weevil, 3-h fumigation with 1.5% SO2 resulted in 96.5% adult mortality and the fumigation with 2.0% SO2 resulted in 99.27% mortality of adults and 87.5% mortality of immature stages. Three-hour fumigations with 1% SO2 resulted in <5% egg survival to adults. The study demonstrated high efficacy of SO2 fumigation against the insects and suggested that SO2 fumigation has good potential for postharvest pest control on stored products.