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

Abstract

BACKGROUND Phosphine‐susceptible or resistant populations of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults were exposed to 0 (control), 1000 and 3000 ppm of phosphine for 15 or 90 min, to estimate behavioral and mobility responses after exposure to phosphine. Knockdown of the exposed individuals after exposure was recorded visually. The total distance moved and velocity of movement were assessed immediately after exposure to phosphine, 2 or 24 h later using a camera coupled with automated video tracking software (i.e. Ethovision®). RESULTS For both species tested, the highest percentage of dead adults was noted at the highest concentration (3000 ppm) for both exposure times. 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 in mobility between susceptible and resistant populations for both species tested. Recovery was much faster in the case of the resistant populations. CONCLUSIONS Changes in movement parameters can be further exploited in assessing the efficacy of different management tactics, such as trapping and sampling. Automated video tracking systems such as Ethovision® can be used to track and record insect behavioral response, providing a more objective measure of insecticide efficacy than visual categorizations. These data shed light on insect mobility and behavioral responses to fumigation treatments in relation to resistance. © 2020 Society of Chemical Industry

Characterizing and predicting sublethal shifts in mobility by multiple stored product insects over time to an old and novel contact insecticide in three key stored commodities

“…In order to impartially observe movement, 23,24,28 video tracking of insects was used. Cohorts of six insects were tracked for 30 min simultaneously in individual, filter paper‐lined petri dishes (85 mm D), consisting of two replicate alive or affected individuals from each insecticide treatment (Diacon IGR+, Gravista or untreated control) described above.…”

“…Thus, insects may be able to deposit eggs in raw grain or in packaged food products inside a warehouse. Furthermore, recent work in the post‐harvest supply chain has documented how movement also may be used as a more impartial indicator of resistance for T. castaneum and R. dominica , with evidence of significant movement by insects even after phosphine fumigation 24 . Taken together, this makes a convincing case for considering sublethal changes in mobility after chemical application.…”

“…In order to impartially observe movement, 23,24,28 untreated control) described above. The petri dishes were backlit using an artistʼs LED lightbox (42 cm wide × 30 cm long, LPB3, Litup, Shenzhen, China) to optimize tracking of insects.…”

“…Historically, the sublethal effects of insecticides have been neglected in post‐harvest IPM 21 but these effects are essential to fully comprehend insecticide efficacy and their most appropriate use in a system. Although sublethal effects may touch on many aspects of insect behavior, reproduction and development, one of the primary factors to consider at food facilities is mobility, often using distance moved and velocity as surrogates 13,18,22–24 . It is well‐known that some stored product insects may disperse long distances, 25 and may be collected far from food facilities 26 .…”

“…Although sublethal effects may touch on many aspects of insect behavior, reproduction and development, one of the primary factors to consider at food facilities is mobility, often using distance moved and velocity as surrogates. 13,18,[22][23][24] It is well-known that some stored product insects may disperse long distances, 25 and may be collected far from food facilities. 26 Mobility is especially important to consider given that insects initially may be affected after exposure to an insecticide, may eventually recover, and move a significant distance before ultimately succumbing to an insecticide.…”