Residual efficacy of an insecticide-coated net for the control of stored product beetles

Highlights

• Residual efficacy of Carifend® was evaluated against four stored product insect species.

• Tribolium confusum was the least susceptible of the species tested.

• Insecticidal effect of Carifend® remained at high levels after 90 days.

• We estimate that this efficacy can be prolonged for more than the storage interval tested here.

Abstract

In the present study, the residual efficacy of an alpha-cypermethrin-coated net (Carifend®, BASF AG, Ludwigshafen, Germany) was evaluated in laboratory studies against four species of stored product insects. The insecticide-treated net was fitted into the bottom of plastic petri dishes, whereas two other sets of dishes (without net, with net without insecticide) served as controls. The insects used in the bioassays were Sitophilus oryzae, Tribolium confusum, Oryzaephilus surinamensis and Prostephanus truncatus. Adults of these species were exposed every 30 d for a total of 90 consecutive days in total. Based on the results, the insecticidal effect of the net remained at high levels during the entire experimental period, indicating its high residual effect. Among the species tested, T. confusum was the least susceptible. Carifend® can be a valuable tool for the protection of stored products against storage insects, and its use can be further examined towards this direction.

Introduction

The use of nets that contain insecticides in stored product protection is not a new approach, and has been evaluated in many application scenarios so far (Gerken et al., 2021; Scheff et al., 2021; Wilkins et al., 2020, 2021). One of these nets that has reached registration and is currently commercially available in many countries is Carifend® (BASF AG, Ludwigshafen, Germany). Carifend® is a polyester, insecticide-coated net that has been registered for the protection of stored tobacco in many parts of the world, and has shown very good results so far (Rumbos et al., 2018; Athanassiou et al., 2019; Paloukas et al., 2020). This net is coated with the pyrethoid alpha-cypermethrin and is used to cover the tobacco boxes after the fumigation treatment in storage conditions (Athanassiou et al., 2019). A similar approach has been used for many years for the protection of humans from mosquitos (Pryce et al., 2018; Mboma et al., 2018; Gleave et al., 2018; Staedke et al., 2020). Apart from the control of pests of public health importance, impregnated or coated nets have been used for many years in crops against agricultural pests in greenhouses (Dader et al., 2015; Arthurs et al., 2018; Agrafioti et al., 2020). Recently, Agrafioti et al. (2020) tested four net formulations coated with SiO₂ nanoparticles, and found that these nets were effective for the control of the black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae).

Carifend® has been recently evaluated under laboratory conditions for the control of the cigarette or tobacco beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae) and the tobacco moth, Ephestia elutella (Hübner) (Lepidoptera: Pyralidae) by Rumbos et al. (2018). In that study, the authors found that, while knockdown of the exposed individuals was low, the nets were effective even after relatively short exposure intervals (Rumbos et al., 2018). Later, Athanassiou et al. (2019) investigated the evaluation of Carifend® in semi-field and field conditions for the protection of stored tobacco from L. serricorne and E. elutella, with success. More recently, this net was evaluated for the control of a wide range of major stored-product insects, indicating that adults of the saw-toothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) and the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) were highly susceptible, but the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) was moderately susceptible (Paloukas et al., 2020).

The residual effect of Carifend® has been tested in the field against L. serricorne and E. elutella, where it was shown that the net can retain its efficacy for several months after its initial deployment (Athanassiou et al., 2019). Nevertheless, while providing an estimation of the net's insecticidal efficacy, these tests were based on the presence of insects in the area of netting deployment and drawn in by pheromone-baited traps. Bioassays that are based on insect exposures to nets may be more accurate for the estimation of the residual effect of Carifend®, i.e. to indicate if Carifend® retains its insecticidal effect for long periods of time. This scenario has not been tested so far for Carifend® in the case of stored product insects. Therefore, the aim of this study was to evaluate the residual effect of this net for the control of four major stored product beetle species, including the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), the confused flour beetle, Tribolium confusum Jacquelin Du Val (Coleoptera: Tenebrionidae), O. surinamensis and P. truncatus.