Abstract
ABSTRACT Bean weevil and maize weevil can cause considerable damage to stored grains. These insects are mainly controlled with synthetic chemical insecticides, which may bring serious problems to human and environmental health. Therefore, this study aimed to evaluate the efficiency of the essential oil of clove [Syzygium aromaticum (L.) Merrill & Perry (Myrtaceae) (origin: Bahia, season Sep.2014-Feb.2015)] in the control of S. zeamais and A. obtectus under laboratory conditions. The essential oil was extracted through the classic hydrodistillation process and its chemical components were identified via gas chromatography. Oil efficiency was tested at the doses of 35, 17.9, 8.9, 3.6, 1.8, 0.4 and 0.2 μL g-1 (derived from a pilot study) for insect control and the LC50 was determined. The results showed that eugenol was the major compound. The essential oil caused mortality of 100% for both species 48 h after treatment with the concentrations of 17.9 and 35 μL g-1. The LC50 for A. obtectus was 9.45 μL g-1, against 10.15 μL g-1 for S. zeamais. The use of clove essential oil represents a promising alternative to be used under storage conditions for the integrated management of stored grains pests.
Highlights
Material and MethodsMany internal and external factors can compromise qualitative and quantitative characteristics of stored grains even after drying
The results of clove essential oil composition characterized by gas chromatography, in this study, indicated eugenol as the major component, which was observed in the study of Cunha et al (2012)
The results show that A. obtectus mortality increases with the increment in the period of exposure to clove essential oil; since there is a response to the increase in concentration, this is perceptible because the concentration of 0.2 μL g-1 does not cause mortality when evaluated for the same period of exposure of the others (Table 2)
Summary
Many internal and external factors can compromise qualitative and quantitative characteristics of stored grains even after drying. Pest insects stand out, which, besides attacking many crop development stages at the field, damage the stored grains, being considered as cross-infestation pests (Scheepens et al, 2011) Among these pests, the bean weevil [Acanthoscelides obtectus (Say, 1831) (Coleoptera: Chrysomelidae)] and the maize weevil [Sitophilus zeamais Motschulsky, 1885 (Coleoptera: Curculionidae)] stand out. The previously mentioned species produce essential oils and their compositions have compounds with insecticide properties, little is known with respect to the effectiveness of these products in the control of pest insects of stored goods. This study aimed to evaluate the efficiency of clove essential oil in the control of S. zeamais and A. obtectus, under laboratory conditions. The LC50 was calculated using the statistical program GraphPad Prism Demo (version 5.0)
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