Immediate and delayed movement of resistant and susceptible adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) after short exposures to phosphine

Authors: Morrison, William - Rob; Brabec, Daniel - Dan; BRUCE, ALEXANDER - University Of Tennessee; ARTHUR, FRANK - Kansas State University; ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2023
Publication Date: 2/15/2023
Citation: Morrison III, W.R., Brabec, D.L., Bruce, A., Arthur, F.H., Athanassiou, C.G. 2023. Immediate and delayed movement of resistant and susceptible adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) after short exposures to phosphine. Pest Management Science. 79:2006-2074. https://doi.org/10.1002/ps.7383.
DOI: https://doi.org/10.1002/ps.7383

Interpretive Summary: Insecticide resistance is a major problem in protecting high-value food commodities after harvest. An underappreciated challenge may be the development of behaviors linked with resistance to phosphine, which is one of the main fumigants to treat infestations in food facilities. Although some insects may be able to detoxify phosphine and its byproducts as a resistance mechanism, movement of insects away from the fumigant followed by subsequent recovery is also a contributing factor to fumigation failures. The purpose of this study was to compare movement patterns of susceptible and resistant populations of red flour beetles after brief exposures to phosphine. In this case, susceptible populations were initially knocked down and significantly less mobile relative to resistant populations. However, twenty-four hours later, insects from both populations were highly mobile. This observation is important for two reasons. First, it is often assumed that individuals that remain mobile after fumigation are resistant. However, this study shows that even susceptible individuals can regain mobility between their initial exposure and when they will ultimately succumb to phosphine toxicity three to five days later and demonstrates that care should be taken when using behavior to assess resistance. Second, it shows the need for monitoring for the development of behavioral resistance in susceptible populations of red flour beetles. Susceptible individuals are still highly mobile for up to twenty-four hours after exposure to phosphine, which can enable them to seek out areas where fumigant concentrations are lower and increase survival. These results support a growing consensus for the need to develop management tactics with quick knockdown and slower recovery times, which can hinder the development of behavioral resistance to fumigants at food facilities.

Technical Abstract: BACKGROUND: During the last decade, the evaluation of certain behavioral attributes has been utilized as an indicator of resistance to phosphine. In this context, an underappreciated challenge may be the development of behavioral traits that are related with resistance to phosphine such as the movement to refugia and recovery of stored product insects after short exposures. Thus, the aim of the current study was to track the movement of phosphine-resistant and -susceptible adults of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), which is a major pest of stored products, after brief exposures to phosphine. Exposures were done for extended intervals to assess the recovery patterns, and how those patterns are related to known resistance to phosphine. A video-tracking procedure coupled with Ethovision software was used to assess movement after exposure. RESULTS: Overall, we found baseline movement was less for phosphine-resistant T. castaneum, suggesting resistance comes at a considerable fitness cost. In the presence of phosphine (1000 or 3000 ppm), there was a much greater reduction in movement for phosphine-susceptible than phosphine-resistant T. castaneum adults immediately after brief 5-min exposures. Twenty-four hours later, these effects were more variable and less apparent regardless of the susceptibility level. CONCLUSIONS: The initial knockdown associated with successful fumigation may just be a temporary state whereafter insects shortly resume movement and may be able to seek out refugia from phosphine, thereby promoting the development of resistance. Our results strengthen a growing consensus that it is the speed to knockdown that truly matters with quick knockdown indicating slow recovery, and a reduced likelihood for the occurrence of resistance.