Abstract
The bean weevil (Acanthoscelides obtectus, Say) is a serious pest of stored bean seeds. Bean weevil control relies heavily on the use of synthetic insecticides. In the search for a sustainable alternative, the residual contact toxicity and anti-oviposition activity of thyme (Thymus vulgaris L.), rosemary (Rosmarinus officinalis L.) and basil (Ocimum basilicum L.) essential oils as well as their dominant components (thymol, ?-pinene, 1,8-cineole and linalool) were tested against A. obtectus adults. Out of the seven tested botanicals, T. vulgaris oil, thymol and linalool exhibited the highest toxic potential (>90% mortality). Females were less susceptible than males. The insecticidal activity of these botanicals was much greater when they were applied on glass compared to direct application to the bean. All tested botanicals reduced oviposition by bean weevil females. T. vulgaris oil, thymol and ?-pinene also deterred bean weevil oviposition, as revealed by a two-choice test. Our research shows that T. vulgaris oil and thymol are promising and sustainable alternatives to synthetic pesticides for protecting stored beans against the bean weevil.
Highlights
The bean weevil Acanthoscelides obtectus (Say) is a cosmopolitan pest of the common bean (Phaseolus vulgaris L.)
The gas chromatography-mass spectrometry (GC-MS) analysis identified a total of 15 components of T. vulgaris, 23 components of R. officinalis and 26 components of O. basilicum environment accompanyEssential oils (EOs)
The efficiency of EOs depends on their chemical composition, which differs among plant species and chemotypes, harvest times and climatic conditions of plant habitats [9]
Summary
The bean weevil Acanthoscelides obtectus (Say) is a cosmopolitan pest of the common bean (Phaseolus vulgaris L.). Its ability to infest beans in the field (preharvest) and in storage (post-harvest), combined with the ability to develop up to 45 larvae in one seed [1,2], make it the most damaging pest in bean granaries It causes severe losses (20-40%) in storage; in developing countries, where weevil management is often poor, it can destroy the entire yield in a few months [3,4,5]. Essential oils (EOs) are complex mixtures of compounds that are produced in various organs (flowers, leaves, bark, roots, rhizomes, fruits and seeds) of aromatic plants. Their role in plants is protective, as antifungal, antibacterial, antiviral and insecticidal activities have been reported.
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