Data from: The chemical communication and monitoring of <i>Sitophilus zeamais</i> is robust to deviations in temperature

<p dir="ltr"><i>Insects</i></p><p dir="ltr">Three strains of <i>Sitophilus zeamais</i> originating from populations sampled in Eastern Kansas in 2022 (FS22), Hudson, Kansas in 2012 (EKS), and Juiz de Fora, Brazil in 2006 (Brazil) and maintained at the USDA Agricultural Research Service’s (ARS) Center for Grain and Animal Health Research (CGAHR) in Manhattan, KS, USA. Colonies were reared on organic whole wheat kernels that had been tempered to 15% grain moisture. To subculture, a total of 100 adult individuals were placed on 200 mL of wheat in a mason jar (capacity: 473 mL) and maintained under constant conditions (27.5°C, 65% RH, 14:10 L:D) in an environmental chamber (136VL, Percival Instruments, Perry, IA) for 7 d to mate and lay eggs. This was necessary because oviposition by <i>S. zeamais </i>is limited at temperatures above 35°C (Throne 1994). After 7 d, adults were removed by sieving with a #10 sieve (2.00 mm; W.S Tyler Inc., Mentor, Ohio) and progeny were either exposed to experimental rearing temperatures (Experiment 1) or maintained at 27.5°C (Experiment 2) until emerging as adults. All experiments employed 1–2-week old adult weevils. When necessary, the sex of individual adults was determined based on the relative size of the rostrum (Richards 1947) and the presence of a small depression on the first abdominal ventrite of males (Sevintuna and Musgrave 1960).</p><p dir="ltr"><i>Experiment 1: Effect of temperature on the volatile emissions of S. zeamais</i></p><p dir="ltr">A 3×3 factorial experiment was conducted to assess the impact of thermal stress on the volatile emissions of <i>S. zeamais </i>and whether <i>S. zeamais </i>responses to thermal stress varied across strains with distinct geographic origins and histories of laboratory culture. After adults were allowed to mate and lay eggs for 7 d at 27.5℃, progeny were transferred to environmental chambers and reared at either 28°C, 32°C, or 36°C (65% RH, 14:10 L:D) until adulthood.</p><p dir="ltr"><i>Volatile Profiling</i></p><p dir="ltr">Solid-phase microextraction (SPME) was employed to concentrate <i>S. zeamais </i>volatile emissions prior to analysis by gas chromatography-mass spectrometry (GC-MS). Cohorts consisting of a mixture of 10 male and 10 female weevils from each treatment were isolated in 20-ml headspace vials containing 2.0 ± 0.1 g of wheat kernels. A small amount of PTFE was applied to the inner wall of each headspace vial to prevent weevils from climbing and coming into contact with exposed SPME fibers. Weevils were housed at their respective rearing temperatures for 24 h, allowing individuals to begin feeding. During this acclimation period, headspace vials were capped but not sealed to prevent oxygen depletion. After the 24 h acclimation period, vials were sealed and a SPME fiber (100 µm PDMS) was exposed to the vial headspace for 24 h. Quantification of sitophilure emission was achieved via comparison to a matrix-matched external standard curve.</p><p dir="ltr">Following extraction, SPME fibers were immediately desorbed at 250°C in the split/splitless inlet of an Agilent 7890B GC equipped with an Agilent Durabond HP-5 column (30 m length, 0.250 mm diameter, and 0.25 µm film thickness). The GC inlet was operated in splitless mode for 3 min, before purging at 15 mL/min. Helium was employed as the carrier gas and maintained at a constant 1.2 mL/min flow and 40 cm/s velocity. The oven was held at 40°C for 3 min before increasing to 80°C at 5°C/min, from 80°C to 300°C at 20°C/min, where it was held for 3 min. Each run took 25 min to complete. The GC was coupled with a single-quadrupole Agilent 5977B mass spectrometer (MS), which scanned between 35 and 550 atomic mass units throughout each run. A mixture containing C8-C20 alkanes was employed to calculate Kovats index for all peaks. Preliminary identification of peaks was achieved by comparing spectral data and Kovats index with references in the NIST 14 library. Data were compiled using Masshunter Unknowns Analysis (Agilent Inc., Santa Clara, CA, USA) and compounds were aligned with the R package uafR (Statton et al., 2024) prior to statistical analysis. To assess whether volatile emissions from wheat kernels accounted for similarities in the volatile profiles of <i>S. zeamais </i>across strain and rearing temperature, the full 3 × 3 factorial experiment was repeated with cohorts of 100 mixed sex weevils in 250 mL reagent jars without wheat.</p><p dir="ltr"><i>Mortality Assessment</i></p><p dir="ltr">As weevils experiencing different levels of thermal stress may experience differential mortality over the course of volatile profiling, the number of actively moving weevils was recorded each day, which was subtracted from the total number of individuals to obtain the number of dead individuals.</p><p dir="ltr"><i>Experiment 2: Effect of temperature on monitoring lure emissions</i></p><p dir="ltr">A 4×3 factorial experiment was conducted to assess the effect of temperature on pheromone lure emission rates over time. <i>Sitophilus zeamais</i> monitoring lures (IL-703, Insects Limited, Westfield, IN; Batch#1579070523, Purchased Sep 2023) were stored at -20°C until needed, then aged for 1, 5, 7, or 14 days at either 28°C, 32°C, or 36°C in separate environmental chambers (Percival Scientific Inc., Perry, IA, USA).</p><p dir="ltr"><i>Headspace collection</i></p><p dir="ltr">At each time point, lure volatile emissions were collected using a headspace collection system (after Van Winkle et al. 2022). An activated carbon filter was employed to remove background volatiles from central air, which was then split between eight lines. Each piece of the system was connected using chemically inert PTFE tubing and fittings. Inline flowmeters (Volatile Collection Systems, Gainesville, FL) were employed to maintain a flow rate of 1 L/min through each line. Volatiles were collected on traps consisting of a drip tip borosilicate glass tube containing 20 mg of Porapak-Q absorbent between a stainless-steel screen (No. 316), borosilicate glass wool, and a PTFE compression seal (Volatile Collection Systems, Gainesville, FL). Volatiles were collected for 24 h, after which compounds were eluted by pushing 150 µL of HPLC-grade dichloromethane (Sigma-Aldrich, St. Louis, MO) through the traps with N<sub>2</sub> gas. The eluent was collected in 2 mL screw-cap GC vials (Item#5191-8121, Agilent Inc., Santa Clara, CA, USA) with 150 μL glass inserts with polymer feet (Item#5181-8872, Agilent Inc.). All samples were sealed with PTFE-backed silicone septa (Item#093640-079-00, Gerstel Inc.) and magnetic screw caps, sealed with PTFE tape, and stored at -20°C prior to chemical analysis. Quantification was achieved via comparison to an internal standard, which consisted of 190.5 ng of tetradecane.<i> </i>Chemical analysis of headspace extracts was as described for SPME samples, except that runs employed an injection volume of 1 µL and a solvent delay of 5.5 min.</p><p dir="ltr"><i>Attraction to aged lures</i></p><p dir="ltr">A 3×3 factorial experiment was conducted to assess whether temperature influences the attraction of <i>S. zeamais </i>to lures over time. Lures were aged either 1, 7, or 14 days at either 28°C, 32°C, or 36°C before being employed in a release-recapture assay. A 87.9 × 47.6 × 32.1 cm (L:W:H) plastic container that was roughened with sandpaper was divided into five 17.58 × 32.1 cm zones (Figure 1). Dome traps (Storgard traps, Trécé inc., Adair, OK, USA) containing 0.4% w/w deltamethrin-incorporated netting (D-terrence, Vestergaard Inc., Lausanne, Switzerland) as a killing agent were located on opposite sides of each container. An aged lure was added to one trap, while the other served as a control. While the position of the lure alternated with each replicate, zones were numbered based on their position relative to the lure with zone 1 always containing the control trap and zone 5 containing the trap with the lure. Twenty-five mixed sex, adult <i>S. zeamais </i>were released in the central zone (3) and allowed to move freely for 24 h, after which the number of weevils in each zone and in each trap was recorded.</p>

Tags: acclimation, aged-lures, agilent-chemstation-software, agilent-data, aging-study, attraction, behavior, behaviorally-based-management, cgahr, chemical-ecology, eastern-kansas, eks, environmental-change, field-strain, gas-chromatography, gc-ms, headspace-collections, headspace-hs, il-703, kansas, ks, lure, maize-weevil, mass-spectrometry, monitoring, mortality, mw, pheromone, pheromone-emissions, sitophilure, sitophilus-zeamais, spme, taxis, temperature, temperature-extremes, thermal-ecology, usa, usda, volatilome
Organization: Department of Agriculture