Assessing the efficacy of microemulsions based on selected essential oils to Bemisia tabaci MED

Essential oils (EO) are promising alternatives that can be applied on the management of insect pests, however its rapid degradation can reduce the activity of these substances in natural conditions. Emulsions based on essential oils can be applied to overcome this drawback. Thus, this work aimed to assess for the first time the bioactivity of emulsions based on the essential oils of Piper marginatum Jacq. (Piperaceae) (PM-EO) and Mansoa alliaceae (Lam.) A.ww H. Gentry (Bignoniaceae) (MA-EO) against Bemisia tabaci Mediterranean (MED) (Gennadius) (Hemiptera: Aleyrodidae) (also named biotype Q). Concentration-mortality bioassays were performed to estimate the lethal concentrations (LCs) on nymphs of B. tabaci MED. The lethal concentrations (LC₅₀s and LC₉₀s) were applied in multi-choice assays to verify the repellent and oviposition deterrent effects. In addition, no-choice assays were performed to assess the ovicidal effects and infestation ability. Finally, the emulsion were diluted in different solvents (water and water + acetone) and applied to verify their efficacy under semifield conditions. According to the particle size, the emulsions were classified as microemulsions. The microemulsions were toxic against nymphs under laboratory and greenhouse conditions and showed ovicidal and repellent effects. The microemulsions also reduced oviposition and inhibited the colonization by B. tabaci MED. Our results reveal the potential of microemulsions based on PM-EO and MA-EO as alternative tools to be applied in the management of B. tabaci MED.