Comparative efficacy of plant derived extracts with the insecticide mospilan on two whitefly species Bemisia tabaci biotype B and Trialeurodes ricini

Abstract

The insecticidal, synergistic, and acetylcholinesterase (AChE) inhibitory effects of plant n-hexane extracts (HEs) were evaluated. The HEs from thyme ( Thymus vulgaris L.) leaves, garlic ( Allium sativum L.) bulbs, and weeping willow ( Salix babylonica L.) leaves were used in comparison with the acetamiprid insecticide (mospilan) against two whitefly species, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B and Trialeurodes ricini (Genn.) (Hemiptera: Aleyrodidae). Furthermore, using the choice test design, the repellent efficacy of three extracts was investigated against whitefly B. tabaci biotype B. The chemical compositions of HEs were identified using gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame-ionization detection (GC-FID) analysis. The main compounds of thyme HE were thymol and geranyl-α-terpinene; in garlic bulbs HE were diallyl sulfide and allyl tetrasulfide; and in weeping willow HE were 6-phenyltridecane, 6-phenyldodecane, and 5-phenyldodecane, while the methylated fatty acids were stearic and palmitic. The HEs of weeping willow and garlic showed the maximum toxicity against B. tabaci, while the HEs of thyme and garlic showed the highest toxicity against T. ricini. Mospilan with HEs resulted in a potentiating effect, with co-toxicity factors ranging between 21.47 for a mixture of garlic HE + mospilan against B. tabaci and 37.65 for weeping willow HE + mospilan against T. ricini. The mix of mospilan + weeping willow HE recorded the highest acetylcholinesterase (AChE) inhibitory effect 48 h after treatment. The highest expulsion effect was recorded by 2% thyme HE, with a repellency index (RI) of 88.22%. The HE of weeping willow at 1% exhibited the highest attractant effect with an RI value of -8.94%. The current research lays the groundwork for the integrated pest management (IPM) of B. tabaci biotype B and T. ricini by employing natural extracts and pesticides blends.