Delayed recovery and sublethal effects on the semiochemical-mediated taxis by khapra beetle after exposure to long-lasting insecticide-incorporated netting

Authors: RANABHAT, SABITA - Kansas State University; Domingue, Michael; MYERS, SCOTT - Animal And Plant Health Inspection Service (APHIS); ZHU, KUN YAN - Kansas State University; Morrison Iii, William

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2025
Publication Date: 3/10/2025
Citation: Ranabhat, S., Domingue, M.J., Myers, S.W., Zhu, K., Morrison III, W.R. 2025. Delayed recovery and sublethal effects on the semiochemical-mediated taxis by khapra beetle after exposure to long-lasting insecticide-incorporated netting. Journal of Stored Products Research. 112:102615. https://doi.org/10.1016/j.jspr.2025.102615.
DOI: https://doi.org/10.1016/j.jspr.2025.102615

Interpretive Summary: Khapra beetle is a destructive insect pest of stored grain that is not currently found in the USA and is considered a quarantine pest. However, it is routinely intercepted at ports of entry into the USA and effective mechanisms to protect goods from becoming infested with this insect pest are needed. Long-lasting insecticide-incorporated netting (LLIN) may be able to protect commodities from infestation by khapra beetle, especially when shipped from countries where khapra beetle has become established. The aims of this study were to evaluate 1) mortality, and 2) movement and foraging behavior by larval khapra beetle after exposure to two LLINs containing different types of insecticides (0.34% alpha cypermethrin or 0.4% deltamethrin). After short-term exposures to both LLINs (5 minutes), mortality was low and many individuals were able to survive. Although mortality was higher after longer term exposures (60 minutes), a substantial number of larvae still survived the treatment. However, mobility was greatly impaired after both short and long-term exposure and the ability to locate food was also impaired after exposure to both LLINs. Notably, ability to trap khapra beetles in monitoring traps used for routine surveillance after they had been exposed to LLIN was also impaired. Thus, although effective at reducing insect movement and preventing infestation of new commodities, the use of LLINs at ports of entry may lead to reduced ability to detect these insects in shipments using conventional traps, which suggests limitations for using LLIN in management for this pest.

Technical Abstract: Trogoderma granarium, or khapra beetle, is a quarantined pest with a history of interceptions in countries where it is excluded. Long-lasting insecticide-incorporated netting (LLIN) may be able to provide additional quarantine security against khapra beetle as a strategy for high-risk commodities. The aims of this study were to evaluate 1) direct lethality, and 2) sublethal effects of exposure to two LLINs on semiochemical-mediated foraging and movement by T. granarium. Direct lethality was examined on larvae after a 5- or 60-min exposure to control netting (without insecticide), a 0.34% alpha-cypermethrin (Carifend, BASF), or 0.4% deltamethrin LLIN (D-Terrence, Vestergaard, Inc.) over 168 h. Sublethal changes in movement were evaluated immediately after a 5-min exposure. Finally, semiochemical-mediated foraging was evaluated 24-h after LLIN exposure by larvae in a release-recapture assay using pitfall traps baited with either no stimulus, food cues, or the sex pheromone for T. granarium. The recovery of larval T. granarium dramatically rose and peaked 72 h–168 h after exposure to LLINs, while the percentage of alive individuals in the control remained consistently high. Larvae spent 6–10% more time in low acceleration and not moving after exposure to alpha-cypermethrin and deltamethrin LLIN compared to the control netting. There was a 6.6-fold higher capture of larvae in traps after exposure to control compared to deltamethrin netting. Elevated response to food cues was suppressed after exposure to LLIN. Overall, there is evidence of significant impacts of LLIN on T. granarium, but high recovery after short exposures and subsequent unresponsiveness to traps suggest limitations for using LLIN in management for T. granarium.