Two grain surface treatment insecticides (deltamethrin and pirimiphos-methyl were evaluated in laboratory assays as a surface treatment for maize to control adult Prostephanus truncatus and Sitophilus zeamais. Both insecticides were applied to 20 g of maize placed in a vial or to the upper one half, one fourth, or one-eighth layer of the maize. Insects were either added to the vials before or after the maize. Mortality, progeny production, and insect damaged kernels (IDK) were then evaluated for each vial. Introduction method (before or after) did not have any impact on any of the variables. Mortality was nearly 100% for all treatments for both insecticides for P. truncatus. Subsequently, progeny production and the number of insect damaged kernels was very low or zero for P. truncatus. Mortality for S. zeamais remained low across layer treatments for deltamethrin. However, S. zeamais was easily controlled by primiphos-methyl. The results of this laboratory study show that while deltamethrin and pirimiphos-methyl has some effectiveness as a layer treatment on a column of maize, efficacy will be dependent on the target species, and the depth of the treated layer, as well as the location on which the insects are present. Resources in this dataset: Resource Title: Grain Layer Experiment with P. truncatus & Sitophilus zeamais File Name: quellhorst_etal_layer_experiment.csv Description: Insect Mortality on Treated Maize and Progeny Production. For each replicate, 500 g of maize were treated with each insecticide or H2O (e.g., control) as described above. Before proceeding with the experiments, the grain moisture content (m.c.) was assessed, using a moisture meter (mini GAC plus, Dickey-John Europe S.A.S., Colombes, France). The standard plastic cylindrical vials of the Laboratory of Entomology and Agricultural Zoology (LEAZ) were used (3 × 8 cm in diameter by height, Rotilabo Sample tins Snap on lid, Carl Roth, Germany). These were filled with 20g of maize. In each vial, we treated either all the grain (1/1), 1/2, 1/4 or 1/8 of the maize with one of the two insecticides (deltamethrin or pirimiphos-methyl) at the labeled rate. We also either placed the insects at the bottom of the vial (before the maize has been added) or at the top (after the maize has been added). Sets A, B, and C were treated with insecticide on separate days. Insects were given 14 days before mortality counts were performed. After this interval, the mortality was assessed. It is difficult to estimate the upper 1/8 etc. of maize, therefore we based our experiments on ratios of 20 g treated, 20 g untreated, 10 g treated with 10 g untreated, 5 g treated with 15 g untreated and 2 g treated with 18 g untreated. The exact quantities of the samples were weighed with a Precisa XB3200D compact balance (Alpha Analytical Instruments, Gerakas, Greece). The upper rings of the vials were treated with Fluon (Northern Products Inc., Woonsocket, USA) to prevent insects from moving away from the grain and or escaping. The top of each vial also had small holes punched to allow ventilation. Each vial then received 10 P. truncatus adults of mixed sex and age from the Tanzania strain or 10 S. zeamais from Brazil. The vials were placed inside incubators set at 30°C and 65% R.H. After the parental mortality count, all adults were removed, and the vials with maize were returned to the incubator at the conditions indicated above. Sixty days later, the vials were opened again to check progeny production and the number of insect damaged kernels (IDK). For each combination, e.g., insecticide × insect species, there were three replicates with three subreplicates (total 3 × 3 = 9 vials or replicates per combination). There were 2 insecticides × 2 insect species × 4 grain treatments (1/1, 1/2, 1/4, 1/8) × 2 insect introduction methods (before or after) × 9 replicates/subreplicates = 288 vials total, 5760 g of maize, 10 insects per vial × 288 = 2880 total (1440 per LAGB and MW). We also had a separate set of vials for the control with no insecticide= 9 × 2 insect species = 18 vials, 360 g of maize, and 180 insects (90 per species).

Insecticide Two insecticides were used in this study: an existing formulation (tradename: Diacon IGR+ R ; Central Life Sciences, Schaumberg, IL, USA), and a new formulation with synergist (tradename: Gravista ). Diacon IGR+ contains 11.4% methoprene and 4.75% deltamethrin, with a label rate of 0.12 kg AI/L and 0.05 kg AI/L. The label rate as a residual surface treatment gives a range of 28.5 mL AI/L−171 mL AI/L H2O to cover 94 m2 for both compounds. We used the maximum labeled rate of 24 mg AI/m2 for deltamethrin and 57 mg AI/m2 for methoprene. This corresponded to 0.3 ml of the formulation in 25 ml H2O, sprayed at the rate of 0.3 ml per 50.3 cm2 arena, using an artist’s air brush (Badger 100 series, Badger Corporation, Franklin Park, IL, US) for each treatment. Each replicate was evenly applied to the concrete dish using a compressor pump. The new Gravista formulation has one labeled rate of 684 ml formulation/L H2O to cover 92.9 m2. To achieve this, we mixed 0.5 ml of the new formulation in 10 ml H2O. This was sprayed at the same rate as the other compound. Distilled water was used for the control arenas at 0.3 mL per arena. The arenas were given 8 h to dry prior to use in experiments. Insects (20 of each species per replicate) were exposed on the insecticide-treated petri dishes for either 4 or 24 h. After exposure, individual Prostephanus truncatus and Sitophilus zeamais were removed and placed into clean Petri dish arenas and evaluated for condition. Using a stereomicroscope (SMZ-18, Nikon Inc., Tokyo, Japan) under 60× magnification, P. truncatus and S. zeamais were classified as alive (moving normally, is able to right itself when flipped over, no twitching), affected (moving sluggishly or erratically, unable to right itself, twitching of antennae or legs may be present), or dead (completely immobile even after prodding) according to prior published definitions (Ranabhat et al., 2022). Dispersal and Mortality To test dispersal capacity to new food patches, a dispersal apparatus was employed. Species-specific cohorts of 20 adults (P. truncatus or S. zeamais) were exposed to Gravista, IGR+, or an untreated control as above for 4 or 24 h, then given 48 h to disperse across 30 or 70 cm standardized sections of PVC pipe (3.175 cm ID). After exposure to insecticide formulations, insects were evaluated for condition after exposure before placing them in the dispersal apparatus. The ends of both sides of the PVC pipe were sealed with mesh (425 μm) to prevent escape. At the far end of the pipe, a hole (2 cm D) was drilled and centered over a glass jar (5 × 6.5 cm D:H) to create a pitfall trap design. The glass jar contained 20 g of whole maize kernels, representing a novel food patch, to induce insects to disperse with food kairomones. Untreated, clean, and uninfested yellow maize was used in the experiments. Grain was sourced from Heartland Mills (Marienthal, KS, USA), and frozen for 72 h prior to use to ensure no prior insect infestation was present. At the end of the sampling period, the number of insects in the jar and their mortality was scored as alive, affected or dead. In addition, the position of each individual was recorded as residing in zone 1 (at the release point), zone 2 (in first half of tube), zone 3 (in second half of tube), or zone 4 (collection jar with maize). In total, there were n = 12 replicate cohorts for each species and combination of distance and treatment. In total, 1,440 P. truncatus and 1,440 S. zeamais were tested in this experiment.

Insecticide Netting In this study, we focused on two types of long-lasting insecticide netting (LLIN) that have been found to be effective for managing various stored product insect pests. One is an LLIN consisting of a polyethylene netting (2 × 2 mm mesh, D-Terrence, Vestergaard, Inc., Lausanne, Switzerland) with 0.4% deltamethrin active ingredient (a.i.), while the second one is Carifend® net (40 deniers with mesh size 97 knots/cm2; BASF AG, Ludwigshafen, Germany) containing 0.34% α-cypermethrin (a.i.). Foundational Model We used a standard Lefkovitch matrix model to project population growth for Tribolium castaneum, with four life stages (e.g., egg, larva, pupa, and adult;(Lefkovitch,1965). In equation (1), the Leftkovitch matrix L matrix (4 × 4) represents the life-stage structure of T. castaneum which has an egg, larvae, pupae, and an adult, where only the adults contribute to the fecundity, F. By multiplying L with the population vector ni(t), where t is time step (e.g., generation) and i is a life stage, we obtain the resultant vector ni(t + 1), which reveals the distribution of individuals across different life stages in the subsequent time period. In equation (1), P1 represents the probability of staying in the egg stage and G1 is the probability of moving from the egg to the larval stage, P2 is the probability of staying in the larval stage, G2 is probability of moving from the larval stage to pupal stage, P3 is the probability of staying in the pupal stage, G3 is probability of moving from the pupal stage to adult, while P4 is the probability of staying in the adult stage (Figure 1). Model Parameterization and Scenarios We simulated population outcomes for up to 15 generations by using the life table data for T. castaneum using the R package popbio. Survivorship, fecundity, and transition information for each stage were derived from the literature (summarized in Table 1). The developmental duration of eggs, larvae, and pupae were 3.82 ± 0.005, 22.81 ± 0.67, and 6.24 ± 0.071 days (Kollros,1944). The average life duration of the adult used in this study was 221.16 days (Park et al., 1961). We used 94 offspring for fertility from the study Park et al.,(1965) and 99% rate of eclosion from pupae to adult. In order to explore the sensitivity of the base model to changes in mortality and fecundity, both of these parameters were systematically varied from near zero to their maximum value given in the base model (e.g., F = 94, P4 = 0.871). The parameters were varied alone or in combination and the resulting population growth was plotted. All plots were created using ggplot2 (Wickham, 2016) in R software (R Core Team, 2022). Three empirical scenarios from the literature were modeled containing estimates of fecundity reduction only, survivorship reduction only, or both fecundity and survivorship reduction when using LLIN (R.V. Wilkins et al., 2021; Gerken et al., 2021;Scheff et al., 2021, Scheff et al., 2023; Table 2). An individual projection matrix was constructed for each of the three scenarios and combinations of the reductions in fecundity, survivorship, or both. Population growth and proportion in each life stage was projected for 15 generations for each case, including the base model. Overall variation and oscillation were calculated to compare trends among proportion of life stages in each case. In order to compare differences in population sizes between cases for all generations and for generation 15 only, population sizes for each generation were bootstrapped 1000 times to provide iterative replication. The bootstrapped data were then compared one case to another using proc ttest in SAS (Version 9.4) for all generations and for generation 15 only. In addition, a sensitivity analysis was performed to determine which stage should be targeted to most greatly affect the population growth after exposure to the netting. Moreover, a mortality function based on empirical data with LLIN exposure collected in the laboratory on T. castaneum was implemented. The three scenarios are derived from: Gerken, A. R., J. F. Campbell, S. R. Abts, F. Arthur, W. R. Morrison, and D. S. Scheff. 2021. “Long-Lasting Insecticide-Treated Netting Affects Reproductive Output and Mating Behavior in Tribolium castaneum (Coleoptera: Tenebrionidae) and Trogoderma variabile (Coleoptera: Dermestidae).” Edited by Rizana Mahroof. Journal of Economic Entomology 114 (6): 2598–2609. https://doi.org/10.1093/jee/toab204. Scheff, D. S., A. R. Gerken, W. R. Morrison, J. F. Campbell, F. H. Arthur, and K. Y. Zhu. 2021. “Assessing Repellency, Movement, and Mortality of Three Species of Stored Product Insects after Exposure to Deltamethrin-Incorporated Long-Lasting Polyethylene Netting.” Journal of Pest Science 94 (3): 885–98. https://doi.org/10.1007/s10340-020-01326-3. Wilkins, R.V., J.F. Campbell, K.Y. Zhu, L.A. Starkus, T. McKay, and W.R. Morrison. 2021. “Long-Lasting Insecticide-Incorporated Netting and Interception Traps at Pilot-Scale Warehouses and Commercial Facilities Prevents Infestation by Stored Product Beetles.” Frontiers in Sustainable Food Systems 4: https://doi.org/10.3389/fsufs.2020.561820. Resources in this dataset: Resource Title: Script for Modeling of LLIN effects on T. castaneum MS File Name: ranabhat_etal_modeling_MS_r_script_final_agdata_commons.R