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  • Author or Editor: Wael M. Khamis x
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Abstract

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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Abstract

Evaluation studies were carried out to simulate realistic field exposures of sulfoxaflor and flonicamid against Aphis gossypii at foraging time of Apis mellifera. Semi-field trials of field rates of sulfoxaflor and flonicamid against A. gossypii laboratory strain at 48 h of exposure had equipollent overall mean of mortality of 62.50 and 63.50%, respectively in season of 2020, likewise 60.50 and 62.50%, respectively in season of 2021. Lethal time values (LT1) had ranges of 51.33–32.46 days for sulfoxaflor and 49.00–39.55 days for flonicamid. Laboratory trials on foraging honeybees (∼21 days old) at 5 h of exposure showed an excellence for sulfoxaflor (5.00%) in overall mean of mortality compared to flonicamid (2.75%) in season of 2020. Likewise, sulfoxaflor (4.75%) surpassed flonicamid (2.75%) in season of 2021. The highest LT1s on honeybees for sulfoxaflor and flonicamid reached 27.45 and 10.94 days, respectively. International Organization for Biological Control classified both insecticides to be harmless on honeybees. Survival foraging bees exposed to LD50s of the tested insecticides had malformed digestive tracts gradually vanished along week of exposure. Suggestions for foliar spray stoppages prior to flowering period were mentioned for both insecticides.

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