Assessing repellency, movement, and mortality of three species of stored product insects after exposure to deltamethrin-inocrporated long-lasting polyethylene netting

Authors: Scheff, Deanna; Gerken, Alison; Morrison, William - Rob; Campbell, James - Jim; ARTHUR, FRANKLIN - Retired ARS Employee; ZHU, KUN YAN - Kansas State University

Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 1/18/2021
Citation: Scheff, D.S., Gerken, A.R., Morrison III, W.R., Campbell, J.F., Arthur, F.H., Zhu, K. 2021. Assessing repellency, movement, and mortality of three species of stored product insects after exposure to deltamethrin-inocrporated long-lasting polyethylene netting. Journal of Pest Science. https://doi.org/10.1007/s10340-020-01326-3.
DOI: https://doi.org/10.1007/s10340-020-01326-3

Interpretive Summary: Long-lasting insecticide-treated (LLIN) netting is a technology that has been effectively used for decades as bed nets to protect against biting insects which could vector diseases. In recent years, technology has been reexplored and has found use in agricultural product protect of select field crops. We took this technology one step further and explored effects of LLIN against three common stored product insects, red flour beetle, rice weevil, and lesser grain borer. The LLIN we used was incorporated with the pyrethroid deltamethrin, which is a synthetic pesticide based on a natural pyrethrin. We first tested whether the LLIN had a repellent effect on our three species of insects using a wind tunnel to gently blow any odor that may be coming from the treated netting towards the insect. We observed no repellent effect. This bodes well for use in stored product protection because these three species will not actively avoid the netting. Next we placed a single adult beetle on arenas containing either all treated netting, untreated netting, or half-treated and half-untreated and recorded their movement on the netting for five minutes to determine if there was a change in movement or behavior of the beetles. We observed differences in distance each species moved, average velocity, and time spent inactive or highly active, but they were more associated with differences in insect species versus being affected by the treated netting. We also did not see any avoidance of netting when the beetles were walking directly on the treated netting, also indicating there is no repellency. Finally we looked at the efficacy of the treated netting on our insect species after a 60-minute exposure to the netting. Approximately 45% or rice weevils and 29% of lesser grain borers were dead 3 days after exposure to the treated netting. The red flour beetles were more resistant to the netting and only had 4% mortality 3 days after exposure and mortality reached 9% at 7 days. What this tells us is that there are differences in susceptibilities to the treated netting, and we need to increase exposure times on the netting to increase mortality. Overall, we observed no repellency or avoidance of the treated netting and we had range of mortality among our species. The warehouses, food processing facilities and grain bins where this netting could be used are full of food volatiles drawing insect towards the food source. At locations were insects could enter a structure are ideal locations to install this netting technology in which insects must cross the treated netting and are exposed to the insecticide which results in a delayed mortality of the insect species.

Technical Abstract: Long-lasting insecticide-treated netting (LLIN) has begun to be used in agricultural product protection. We investigated the effect of a deltamethrin-incorporated LLIN on three stored product insects, Tribolium castaneum (Herbst), red flour beetle, Rhyzopertha dominica (F.), lesser grain borer, and Sitophilus oryzae (L.), rice weevil. Long-distance repellency was assessed in a wind tunnel for adults of each species, but no repellency was observed. Insect movement and behavior was assessed by observing the movement of adult beetles on treated and untreated netting during a 5-min period for distance traveled, average velocity, mobility, and time spent on each netting type. Tribolium castaneum spent the most time on the netting, was highly mobile and traveled a greater distance. Sitophilus oryzae and R. dominica spent significantly more time immobile and lower velocity. Efficacy of LLIN was tested by exposing adults for 60-min, removing, and holding with or without food, and monitoring for mortality up to 7 d. All S. oryzae and R. dominica were either affected or dead at all post exposure times. The number of affected and dead adult T. castaneum combined 7 d after exposure was 95% or 42%, with or without food respectively, and 52% of affected adults were able to recover when food was present. Overall, LLIN had no repellency or negative effect on insect movement, which increases the probability of lethal exposures of adults from walking on the netting. LLIN can be adopted in existing integrated pest management (IPM) programs for food processing facilities to prevent stored product insect infestations.