Spillage and food dust do not decrease efficacy of long-lasting insecticide-incorporated netting against stored product insects

Abstract

The foundation of many postharvest integrated pest management (IPM) programs is proper sanitation. However, there may be deviations from this due to the effort, time, and cost required to keep a facility clean. Long-lasting insecticide-incorporated netting (LLIN) has been used successfully to augment post-harvest IPM programs, but has not yet been investigated for its role in supporting sanitation. Here, we investigated the use of LLIN to spot treat spillage and how food dust deposition may alter LLIN efficacy against Tribolium castaneum and Rhyzopertha dominica. After immersing 0.34 % alpha-cypermethrin LLINs in flour, we found no significant changes in adults of both species classified as alive, affected, and dead compared to undipped LLINs. We found slightly more recovery by T. castaneum after exposure to 0.4 % deltamethrin LLIN in the presence of food dust compared to when it was absent, but there was no effect on recovery for R. dominica. When a layer of LLIN was used to cover spillage, we found statistically equivalent numbers of affected and dead individuals induced compared to when spillage was absent. After holding spillage for 6 weeks, no larvae and 87 % fewer pupae were produced by T. castaneum after exposure to a layer of alpha-cypermethrin LLIN for 48 h, compared to netting without insecticide. Finally, we found a 2.5 cm strip of LLIN sufficiently impeded the dispersal of R. dominica on a site of spillage, but this was not the case for T. castaneum. Overall, these results suggest the use pattern for LLIN could be expanded, and that food dust will minimally affect LLIN efficacy against stored product insects, most likely due to the high concentration of the active ingredient in LLIN.