Volume 71, September 2015, Pages 31–36
Highlights
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- Sitophilus zeamais and Tribolium castaneum are important pests of stored grains.
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- EOs of Lippia alba chemotypes and their major monoterpenes were tested here.
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- Carvone chemotypes were more toxic than citral chemotypes for both species.
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- The compounds were highly repellent for T. castaneum.
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- Carvone rich EOs and carvone isolated are alternatives to control these insects.
Abstract
The insects Sitophilus zeamais and Tribolium castaneum
cause losses in stored grains and are considered pests of wide
distribution and global significance. In the present study, we evaluated
the toxicity and repellency of essential oils of different Lippia alba
genotypes (carvone chemotypes LA-13 and LA-57 and citral chemotypes
LA-10 and LA-44) and their major monoterpenes, carvone and citral, on S. zeamais and T. castaneum.
Toxicity bioassays by exposure of the insects on treated filter paper
were performed to determine the concentration and lethal time.
Repellency tests were performed using the most toxic compounds according
to the toxicity bioassays. The carvone chemotypes were more toxic than
the citral chemotypes for both species: for S. zeamais, the LC50 values were 15.2 μL/mL (LA-13) and 16.7 μL/mL (LA-57) and for T. castaneum, the LC50 values were 28.7 μL/mL (LA-13) and 19.7 μL/mL (LA-57). Isolated carvone (LC50 = 8.8 μL/mL) was more toxic than citral. For S. zeamais, the monoterpene citral had the lowest lethal time (LT50 = 6 h), whereas for T. castaneum, the monoterpenes carvone and citral showed a more rapid toxicity (LT50 = 7.3 h). The compounds tested were highly repellent to T. castaneum; however, no repellency’s effect was observed against S. zeamais,
except for LA-13 chemotype. The essential oils from the carvone
chemotype and the monoterpene carvone have potential for the development
of natural insecticides against stored grain insects S. zeamais and T. castaneum.
Graphical abstract
Keywords
- Brazilian lemon balm;
- Genotypes;
- Essential oils;
- Carvone;
- Citral;
- Insect pests
Copyright © 2015 Elsevier B.V. All rights reserved.
