AUTHOR=Lak Fatemeh , Zandi-Sohani Nooshin , Ghodoum Parizipour Mohammad Hamed , Ebadollahi Asgar 

TITLE=Synergic effects of some plant-derived essential oils and Iranian isolates of entomopathogenic fungus Metarhizium anisopliae Sorokin to control Acanthoscelides obtectus (Say) (Coleoptera: Chrysomelidae)

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1075761

DOI=10.3389/fpls.2022.1075761

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>The bean weevil, <italic>Acanthoscelides obtectus</italic>, is one of the most important pests of the common bean, <italic>Phaseolus vulgaris</italic>. The pest attacks <italic>P. vulgaris</italic> seeds while they are still in the field. However, the damage continues during storage, where it causes the most significant losses.</p></sec><sec><title>Methods</title><p>The present study was conducted to evaluate the insecticidal activity, and synergic effects of three essential oils (EOs) extracted from fennel (<italic>Foeniculum vulgare</italic>), tarragon (<italic>Artemisia dracunculus</italic>), and lavender (<italic>Lavandula angustifolia</italic>), and three isolates from an entomopathogenic fungus (EPF), <italic>Metarhizium anisopliae</italic>, including IRAN2273C, IRAN2252C, and IRAN1018C against the adults of <italic>A. obtectus</italic>. The effects of EOs were also evaluated on mycelial growth and conidiation of the fungal isolates.</p></sec><sec><title>Results and Discussion</title><p>The results showed that all the EOs and the EPF exhibited insecticidal activity against <italic>A. obtectus</italic>. According to calculated LC<sub>50</sub>, <italic>L. angustifolia</italic> (1.2526 µl/l) and <italic>F. vulgare</italic> (0.9247 µl/l) EOs caused significantly higher mortality than <italic>A. dracunculus</italic> (3.1980 µl/l) against <italic>A. obtectus.</italic> The results of the pathogenicity of M. <italic>anisopliae</italic> isolates revealed that all isolates had insecticidal activity against <italic>A. obtectus</italic>. The cumulative mortality of insects varied from 59.12% in IRAN1018C to 80.86% in IRAN2273C. According to the compatibility test results, all EOs were compatible with fungal isolates except for <italic>A. dracunculus</italic>, which was toxic to the IRAN2252C isolate and showed incompatibility. The mortality of <italic>A. obtectus</italic> adults differed significantly among combined treatments of EOs and <italic>M. anisopliae</italic> isolates. According to the calculated synergic ratio, combinations of essential oils and fungal isolates had additive or synergistic effects on the mortality of <italic>A. obtectus</italic>. Based on the present findings, <italic>A. obtectus</italic> adults were susceptible to fennel, and lavender EOs, and their mortality was amplified when the EOs were combined with <italic>M. anisopliae</italic> isolates. These results can be helpful for the integrated management of <italic>A. obtectus</italic> during storage.</p></sec>