Appraising the role of anti-thermal activity of beta-cyclodextrin on selective insecticides against Thrips tabaci (Thysanoptera: Thripidae)
2022
Khamis, Wael M. | Abdel-Moety, Ehsan M.
Evaluation studies investigated the leverage effects of beta-cyclodextrin (β-CD) on the long-termed toxicity of cypermethrin 25% EC, sulfoxaflor 24% SC, acetamiprid 20% SL and chlorfenapyr 24% SC against adults of Thrips tabaci laboratory strain (Thysanoptera: Thripidae) (Lindeman, 1889) from 8 up to 40 °C. Laboratory studies showed no toxicity for β-CD alone at all tested concentrations. Concentrations of β-CD at 1.25 and 2.50 gm L⁻¹ had potent leverage effects on the LC₅₀s of cypermethrin within 30–35 °C and sulfuxoflor at 40 °C. β-CD at 0.5 gm L⁻¹ had no leverage effect on tested insecticides. All the tested concentrations of β-CD decreased the toxicity of acetamiprid. Semi-field trials (≥28 °C) along 12 days declared that β-CD (equivalent to 1.25 gm L⁻¹) increased the overall mean mortality percentages of 0.5 FRs of cypermethrin (73.08%) and sulfoxaflor (54.74%) compared to their 0.5 FRs alone of 63.70 and 44.30%, respectively in season 2020. While in season 2021, only cypermethrin at 0.5 FR + β-CD (74.45%) surpassed its 0.5FR (61.83%). Lethal times (LT₅₀) values in semi-field trials showed a prolonged residual toxicity periods for the 0.5 FRs of cypermethrin + β-CD (8.58 days) and sulfoxaflor + β-CD (4.80 days) compared to their 0.5 FRs of 6.65 and 3.24 days, respectively in season, 2020. Furthermore, LT₅₀ values of the 0.5 FRs of cypermethrin + β-CD (9.02 days) and sulfoxaflor + β-CD (7.34 days) exceeded their 0.5 FRs of 6.24 and 4.07 days, respectively in 2021. Thus β-CD could realize leverage efficacy and longer-termed toxicity for cypermethrin and sulfoxaflor in high temperatures.
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