Data from: Effects of synergists on the efficacy of long-lasting insecticide-incorporated netting against Tribolium castaneum (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (Coleoptera: Bostrichidae)

Experimental Insects

Adult Tribolium castaneum and Rhyzopertha castaneum were obtained from insect colonies kept at the United States Department of Agriculture (USDA) Center for Grain and Animal Health Research in Manhattan, Kansas. Tribolium castaneum was continuously reared on 95% unbleached, organic wheat flour with 5% brewer’s yeast added, while R. dominica was reared on organic wheat, and both were held in an environmental chamber (Percival Scientific, Model CTH-811, Perry, IA, USA) set at a temperature of 30 °C, relative humidity (RH) of 65%, and a 16/8 h light/dark photoperiod. For the bioassays below, 3- to 4-week-old T. castaneum and R. dominica adults were used.

Synergist-coated Vials

Insecticide synergists tested in the bioassays were: piperonyl butoxide (PBO, Tokyo Chemical Industry Co. Ltd., Tokyo, Japan), diethyl maleate (DEM, Thermo Scientific Chemicals, Waltham, MA, USA), and triphenyl phosphate (TPP, Sigma-Aldrich, St. Louis, MO, USA).  PBO, DEM, and TPP were dissolved in acetone, separately, and the concentrations used for them were all 0.1 mg/ml. Glass scintillation vials (27 × 61 mm, D × H, Wheaton Science Products, Millville, NJ, USA) were coated with 0.5 ml of synergist solution by rolling the vials on a Roto-Torque Heavy Duty Rotator (Model 7637, Cole-Parmer Instrument Company, Vernon Hills, IL, USA) to spread the synergist across the inner surface until all visible signs of liquid had disappeared. The vials were then left open to evaporate the acetone residues. In parallel, vials were coated with 0.5 ml of acetone as a control.

Long-lasting Insecticide-incorporated Netting (LLIN)

Carifend^® LLIN incorporating 0.34% (w/w) alpha-cypermethrin (BASF, Ludwigshafen, Germany) was used in this study. This netting was cut into squares and secured to the bottoms of square Petri dishes (100 × 100 × 15 mm, L × W × H, VWR, Radnor, PA, USA) as LLIN exposure arenas.

Effects of Synergists on LLIN against T. castaneum and R. dominica

Synergists and LLIN exposure bioassays for T. castaneum and R. dominica adults were conducted as below. Twenty adults were pre-exposed in a glass scintillation vial coated with one of the three synergists (PBO, DEM, TPP, or acetone as a control) for 1 h, and then transferred to a LLIN exposure arena. For T. castaneum, twenty adults were exposed to LLIN for 6, 12, 24, 48, 72, 96, 120, 144, and 168 h, respectively, and then examined for adult condition (unaffected, affected, and dead). For R. dominica, preliminary experiments showed that adults were very susceptible to LLIN, so twenty adults were exposed to LLIN for 0.5, 1, 2, 6, 12, 24, and 48 h, respectively. The adults were then transferred to a 35 × 10 mm Petri dish (Falcon, Franklin Lakes, NJ, USA) and adult condition was examined after 24 h. T. castaneum and R. dominica adults were observed and recorded as unaffected if they were active and behaving normally with coordinated walking and species-specific movements; affected if they had uncoordinated waliking and sluggish movements or were on their backs with legs twitching, and/or could not right themselves after being prodded (i.e., knocked down); finally, recorded as dead if they were completely motionless even after prodding. There were 4 replicates for each treatment combination of synergist type × LLIN exposure time.

Effects of Food on Efficacy of Synergists and LLIN Combined Exposures in T. castaneum and R. dominica

Twenty adults were pre-exposed in a vial coated with PBO, DEM, TPP, or acetone as a control for 1 h, and then exposed to LLIN for 72 h (T. castaneum) and 1 h (R. dominica). After exposure, the adults were transferred from LLIN exposure arena to a recovery arena, consisting of Petri dish (35 × 10 mm, D × H, Falcon, Franklin Lakes, NJ, USA) with 0.5 g of wheat flour or without flour as a control. Adult condition was assessed as number of unaffected, affected and dead at 1, 3, 5, and 7 d post-exposure. The delayed mortality and recovery rates were expressed as percentages, the number of dead and unaffected individuals divided by the total number of adults for the sample, respectively. There were 4 replicates for each combination of synergist type × post-exposure time × food availability. During exposure and recovery, insects were kept in an environmental chamber under the same conditions as described above.