Scaling recovery of susceptible and resistant stored product insects after short exposures to phosphine by using automated video-tracking software

Authors: AGRAFIOTI, PARASKEVI - UNIVERSITY OF THESSALY; Brabec, Daniel - Dan; Morrison, William - Rob; Campbell, James - Jim; ATHANASSIOU, CHRISTOS - UNIVERSITY OF THESSALY

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2020
Publication Date: 3/1/2021
Citation: Agrafioti, P., Brabec, D.L., Morrison III, W.R., Campbell, J.F., Athanassiou, C.G. 2021. Scaling recovery of susceptible and resistant stored product insects after short exposures to phosphine by using automated video-tracking software. Pest Management Science. 77(3):1245-1255. https://doi.org/10.1002/ps.6135.
DOI: https://doi.org/10.1002/ps.6135

Interpretive Summary: There is increasing resistance by a variety of stored product insect species to phosphine, one of the main fumigants used to control insects in commodities. There are a variety of methods of assessing resistance to phosphine, and past work has used observations of knockdown as a quick measure of efficacy, but this response is not consistently defined and applied across different observers and can be difficult to accurately determine based on short term visual observations. Here, we evaluated whether characterization of insect movement pathways could be used as a more objective surrogate indicator of resistance. Susceptible and phosphine-resistant lesser grain borer and red flour beetle, two important, damaging, and cosmopolitan stored product insects, movement was digitally recorded and analyzed at different time points after exposure to phosphine, and it was demonstrated that mobility of individuals corresponded to resistance. Thus, we found that we can reliably use increasing mobility as an indicator of increasing resistance after fumigation for stored product insects in the US using automated software. Overall, this may be used to help more objectively quantify resistance by insects to chemical control procedures, and help food facility managers to more fully understand the efficacy (or lack thereof) by their integrated pest management tactics.

Technical Abstract: Susceptible or phosphine-resistant strains of adult Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) were used in our experiments. Adults were exposed to 0 (control), 1000 and 3000 ppm of phosphine for 15 or 90 min. The mobility of each population after using phosphine was tested. The total distance moved and velocity of movement were assessed immediately after exposure to phosphine, 2 h, or 24 h later using a camera coupled with automated video tracking software (e.g. Ethovision). For both species tested, the highest percentage of immobilized adults was noted at the highest concentration tested (3000 ppm) for both exposure times. Specifically for T. castaneum, total distance moved and velocity decreased as the concentration increased for the susceptible population, whereas there was significant variation among individuals in the resistant population. For R. dominica, the distance moved was reduced at the highest concentrations. Individuals of R. dominica moved less than those of T. castaneum and there were significant differences between susceptible and resistant populations for both species tested, and recovery was much faster in the case of the resistant populations. Differences in movement parameters are key indicators that can be further exploited in different management tactics, such as trapping and sampling. Automated video tracking systems such as Ethovision can be used to track and record insect response providing objective measures of insect movement. These objective data provide clearer measures of insect responses to compare potential efficacy of fumigation treatments and insect control practices.