Plant-derived benzoates are known to have insecticidal and repellent activities, however, these effects have been evaluated thoroughly in only a few groups of insects. In this study, the insecticidal activities of three commercially available benzoates, methyl benzoate (MB), ethyl benzoate (EB), and vinyl benzoate (VB), were assessed against the cotton aphid, Aphis gossypii Glover, and its lacewing predator, Chrysoperla carnea Stephens. MB showed the highest contact toxicity against nymphs and adults of A. gossypii, as compared to those of EB and VB. Treatments with 1% MB, EB, and VB were 100.0%, 93.0% and 60.0% effective, respectively, against third-instar nymphs and 100.0%, 69.0%, and 39.0% effective, respectively, against adults of A. gossypii, as evaluated 24 h after application. A mixture of MB + EB showed higher efficacy than other benzoate combinations against A. gossypii. The efficacy of MB, EB, and VB against A. gossypii on cucumber plants under greenhouse conditions was 93.7%, 68.5%, and 56.6%, respectively. In addition, treatments with 1% MB, EB, and VB were 20.0%, 24.0%, and 12.0% effective, respectively, against first-instar larvae and 6.7%, 13.3%, and 6.7% effective, respectively, against adults of C. carnea at 24 h after treatment. Our results showed that the tested benzoates were less toxic to the predator C. carnea than to the pest A. gossypii. In addition, the aphid population was significantly lower in a treatment combining predation by C. carnea followed by use of 1% MB, compared with treatments of either 1% MB or predators alone. This study suggests that plant-derived benzoates are potential biopesticides for aphid control and are compatible with natural enemies in integrated pest management.
Keywords: Aphids; Benzoates; Natural enemies; Plant-derived pesticides; Predators.
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