Exposure to a Novel Insecticide Formulation on Maize and Concrete Reduces Movement by the Stored Product Pests, Prostephanus truncatus (Horn) and Sitophilus zeamais (Motschulsky)

Abstract

Two major stored products pests of maize are the Prostephanus truncatus (Horn) (larger grain borer) and Sitophilus zeamais (Motschulsky) (maize weevil). Under climate change, P. truncatus may be expected to shift its distribution northward farther into the United States (US). Thus, there is a critical need to develop diversified chemical control tools in the post-harvest supply chain for these two species. In this study, we investigated the efficacy of a novel insecticide formulation, containing the insect growth regulator, S-methoprene, combined with the pyrethroid, deltamethrin and the synergist piperonyl butoxide (Central Life Science, Schaumberg, IL, US), compared to the existing commercial standard formulation without synergist, and controls at inducing direct mortality and sublethal changes in movement on treated grains as a grain protectant, and on concrete as a surface treatment. Mortality of adults was assessed visually, while movement was tracked with a network camera coupled with Ethovision software that automatically recorded velocity and distance moved by both species, after continuous exposure on treated material for 4–168 h. The novel formulation significantly induced mortality while reducing distance and velocity moved by multiple-fold compared to controls for exposed adults even after relatively brief exposure periods. In fact, the novel formulation was just as effective as the older formulation, but used only a fraction of the active ingredients, thus it may be more cost-effective. Overall, the novel insecticide formulation is a promising tool for controlling S. zeamais and P. truncatus in bulk storage and around other food facilities.

Efficacy of deltamethrin and pirimiphos-methyl in proportionally layer-treated maize against the larger grain borer and the maize weevil

“…Prostephanus truncatus was the more susceptible species than S. zeamais to both deltamethrin and pirimiphos-methyl, which is also commonly observed in other studies, especially for deltamethrin (Quellhorst et al 2022). In our study, mortality for P. truncatus adults exposed to deltamethrin was 97% or greater regardless of whether the insects were placed in the vials before or after the placement of maize.…”

“…The insect was thought to have originated from Mexico, Central America, and Northern South America (Hodges et al 1983). Most of the efforts to control P. truncatus have been focused on the use of a wide range of insecticides, with varied results (Golob 2002, Rumbos et al 2013, Quellhorst et al 2021, 2022). However, there are disproportionally few published data on the use of contact insecticides and fumigants for the management of this species, as compared with the vast majority of other major stored product insect species (Quellhorst et al 2021).…”

Sub-Lethal Effects of Pirimiphos-Methyl Are Expressed to Different Levels in Wings of Three Stored-Product Coleopterans: A Geometric Morphometrics Investigation

“…Furthermore, it can be hazardous to humans due to allergies caused by the contamination of commodities from the secretion of quinones [ 7 , 8 ]. Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) causes extensive and irreparable damages to stored dried tubers of cassava and maize [ 9 , 10 ]. It was accidentally introduced to Africa from Central America in the late 1970s [ 11 ].…”

Insect-resistance test of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) on several maize hybrid lines

“…The longer the storage, the higher the population. Warehouses that are too dark and humid can trigger the growth of micro-organisms that destroy seeds [11,12] Several techniques to control the maize weevil have been studied previously such as new technologies and traditional technologies using plant extract [13,14], combination of biotic controlling agent [15,16], abiotic control [12,17], insecticide [18], and genetic resistance techniques [19,20,21]. Based on those techniques, the selection based on the resistance level to the S. zeamais is important to understand and can be used in breeding programs [22].…”