Data from: Direct lethality and time-delayed sublethal effects of multiple types of insecticide netting against stored product insects

Experimental Insects

The field strains of T. castaneum and R. dominica (F.) were used in this study. The former originates from Eastern Kansas in 2012, and the latter is also from Eastern Kansas but from 2019. For all species, four to eight-week-old adults were used. Rearings were kept at the USDA Center for Grain Animal Health Research in Manhattan, KS. Tribolium castaneum was reared on a mixture of 95% unbleached, organic flour and 5% brewer’s yeast, while R. dominica was reared on tempered organic whole wheat. Colonies were maintained at 27.5°C, 65% RH, and 14:10 or 16:8 (L:D) h photoperiod.

Treatments

Treatments included exposure to three different types of long-lasting insecticide-incorporated netting (LLIN). These consisted of 1) Carifend®, LLIN with 0.34% alpha-cypermethrin (40 deniers, BASF, Ludwigshafen, Germany), 2) D-Terrence, LLIN with 0.4% deltamethrin (2 × 2 mm mesh, Vestergaard SA., Lausanne, Switzerland), and 3) 8% etofenprox LLIN (AgBio, Inc, CO, USA), and for control, we used netting identical to the Carifend or Vestergaard netting but lacking insecticide.

Direct Lethality Assessments

Cohort of 20 mixed-sex adult beetles were exposed for 5, 60, or 120-min intervals on netting affixed to a 9 × 9 cm2 petri dish in the laboratory. After exposure, we took the evaluated condition after 0, 24, 72, or 168 h (as alive, affected, or dead condition, according to the definitions described in Ranabhat et al. (2022) in Petri dishes without netting containing 8.5 cm D filter paper. Briefly, living adults were defined as moving with normal speed and activity and able to right themselves if flipped. By contrast, affected adults exhibited sluggish or drunken movements, could not right themselves if flipped, and some or all of their limbs exhibited twitching. Dead adults were completely immobile. For post-exposure treatment, adults were held under the same environmental chamber conditions as the colonies but without supplemental food after exposure. We performed a total of n = 4 replications per treatment combination for each species.

Baseline Mobility Assay after Exposure to LLINs

Based on the observation of the lethality assay, we focused our baseline mobility assay on Carifend® and D-Terrence LLIN. Using only alive adults, we assessed their movement in six individual Petri dishes (100 × 15 mm D: H) that consisted of a filter paper (85 mm D, Grade 1, GE Healthcare, Buckinghamshire, United Kingdom) lining. Treatments included a negative control (e.g., filter paper only), one of the two LLINS, or an identical netting to the Carifend or Vestergaard netting but without insecticide (e.g., as a positive control). Their movement was tracked for 60-min using a network camera (GigE, Basler AG, Ehrenburg, Germany) affixed 80 cm above the dishes. The Petri dishes were backlit using a LED light box (42 × 30 cm W: L, LPB3, Litup, Shenzhen, China) to increase contrast and affixed in place with white foam board. The video was streamed to a computer and processed in Ethovision (v.14.0, Noldus Inc., Leesburg, VA). The program automatically calculated the total distance moved (cm) and the instantaneous velocity (cm/s) over the 60-min period for each adult. Each adult was considered a replicate and was never used more than once. In total, n = 18 replicates were performed per treatment combination.

Comparison of Sublethal Effects among LLINs

For the sublethal movement assay, mixed-sex adult beetles were exposed to the Carifend®, D-Terrence LLIN, or control net as mentioned above. Cohorts of 5–10 adults were exposed for 5- or 60-min intervals on LLINs affixed to a 9 × 9 cm2 Petri dish in the laboratory. After exposure, the effects of the LLINs on adult movement were assessed either immediately or after 72 h in Petri dishes under the same environmental chamber conditions as the colonies but without supplemental food and then assayed using the video-tracking system described above by using Ethovision software. Only adults classified as alive or affected as defined in Ranabhat et al. (2022) were used in this assay. In total, n = 16–20 replicates were performed per treatment combination.