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This study presents an attempt to evaluate the acaricidal activity of two medicinal plants,Helichrysum bracteatum(Asteraceae) and Salvia officinalis(Lamiaceae) against Tetranychus urticae Koch and for the first time to its predator, Stethorus gilvifrons adult females under laboratory conditions.The ethanolic leaf extracts of H. bracteatum [HbLEEtOH70%] and S.officinalis [SoLEEtOH70%] were assessed for their direct toxicity against T.urticae and S.gilvifrons adult females. Then both extracts were assessed for their effects on the egg-laying capacity, repellent and oviposition deterrent effects of T.urticae adult females, as well as their direct effects on T.urticae eggs. The chemical characterization of both extracts was conducted to investigate their bioactive components by gas chromatography (GC-MS). Based on acute toxicity, results showed that HbLEEtOH70% displayed the highest acaricidal activity (LC50=1.27%) followed by SoLEEtOH70%(3.39%) against T.urticae adult females. Whereas, against S. gilvifrons adult females, SoLEEtOH70% was less toxic (LC50=37.06%) than HbLEEtOH70% (LC50=0.76%).Our results revealed that only HbLEEtOH70% had a significant effect on the egg-laying capacity of T.urticae adult females. According to the repellent index (RI), the HbLEEtOH70% and SoLEEtOH70% were classified as repellent.Both extracts revealed a potent ovicidal effect, where the egg hatching percentage was 48.75±15.38 and 45.34±11.73% for HbLEEtOH70% and SoLEEtOH70%, as compared to their control groups 98.81±0.7%,respectively. GC-MSanalysis showed that phytol was the major component of HbLEEtOH70% and SoLEEtOH70%. The current study confirmed the potent acaricidal effect of H.bracteatum and S.officinalis leaf extract against T.urticae. Thus, the S.officinalis leaf extract was the safe acaricidal product suitable for use in integrated pest management strategies as it was safe for S.gilvifrons. |
