The behavioral response to the putative necromones from dead Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in traps by conspecifics as a function of density and time since capture

Authors: HARMAN, RACHEL - Orise Fellow; Morrison, William - Rob; BRUCE, ALEXANDER - University Of Tennessee; RANABHAT, SABITA - Kansas State University; QUELLHORST, HANNAH - Kansas State University; WILKINS, RACHEL - Kansas Department Of Agriculture; Campbell, James - Jim; Gerken, Alison

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2023
Publication Date: 12/1/2023
Citation: Harman, R.H., Morrison III, W.R., Bruce, A., Ranabhat, S., Quellhorst, H.E., Wilkins, R.V., Campbell, J.F., Gerken, A.R. 2023. The behavioral response to the putative necromones from dead Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in traps by conspecifics as a function of density and time since capture. Environmental Entomology. 52(6):1020-1032. https://doi.org/10.1093/ee/nvad098.
DOI: https://doi.org/10.1093/ee/nvad098

Interpretive Summary: Long-term trapping programs are used to monitor population levels of stored product insects so that accurate and rapid pest management decisions can be deployed when needed. Red flour beetle is a highly successful stored product pest of flour mills and food facilities, and is frequently monitored using a commercial pitfall trap baited with pheromones and food oils. However, as beetles are caught in the trap, they may change the attractiveness of the trap by releasing volatile compounds as they die that could attract or repel insects from the trap. By varying the number of dead beetles and the time that they were present in trap food oil, we demonstrated that although there were some significant behavioral changes under certain conditions, overall behavioral responses of red flour beetles were similar regardless of the number of dead individuals or length of time they were present in the traps. By measuring the volatile compounds in the air above the oil, we also showed that the volatile chemical compositions were similar whether dead beetles were present or not. Similar results were obtained when different populations of red flour beetle were used, including one that was recently caught from the field. Given that behavior and relative volatile composition was generally unaffected by the presence of dead individuals, repellence from, or increased attraction to, pitfall traps due to the accumulation of dead individuals and changing composition of food oil is likely not a major issue in most environments. Thus, long-term monitoring programs may be robust in their interpretability over time, boosting confidence in trap capture data.

Technical Abstract: Long-term trapping programs of stored product pests provide information for timely and accurate pest management. Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is a highly successful external-infesting grain pest, and is frequently monitored using a commercial pitfall trap that combines pheromonal and kairomonal stimuli. However, an often overlooked component of lure-based traps is the potential for the volatile plume to change over time as individuals are captured. These now dead insects, may then release necromones altering the captures of conspecifics. In this study, we evaluated changes in 1) the behavior of T. castaneum and 2) the relative change in volatiles over time since dead insects were added and among different densities of dead conspecifics in a commercially-available kairomone oil. We used multiple behavior assays, including wind tunnel, release-recapture, and two-way olfactometer and performed chemical analyses via headspace collection and gas chromatography coupled with mass spectrometry. Tribolium castaneum response to the commercially-available kairomone lure did not vary with density of conspecifics between 4–40 adults after 24 h or 96 h, or with time of seeding over 1–96 hours or 8–11 days prior. Strains collected in 2012 and 2019 were tested to rule out strain-specific differences. Oil rancidity was also ruled out as a factor contributing to the response of T. castaneum. The relative volatile composition was generally stable among the treatments despite using different seeding densities and seeding times. Given that attraction and relative volatile composition was generally unaffected by prior captures, long-term monitoring programs may be robust in their interpretability over time.