Abstract

Essential oils have emerged as an alternative to synthetic insecticides in the control of stored grain pests. The toxicity and repellency of the essential oils of four basil cultivars and three basil hybrids and the monoterpenes linalool, citral, and (E)-methyl cinnamate were evaluated in the stored grain pests Callosobruchus maculatus and Sitophillus zeamais. The essential oils of the cultivar Genovese and the hybrid 'Genovese' x 'Maria Bonita' were more toxic to C. maculatus. Conversely, the essential oils of the cultivar Sweet Dani and the hybrid 'Cinnamom' x 'Maria Bonita' were more toxic to S. zeamais. Among the monoterpenes, (E)-methyl cinnamate was the most toxic to both pests, taking 0.14 and 0.34 µL.mL-1 to kill 50% of the C. maculatus and S. zeamais populations, respectively. All essential oils from cultivars, hybrids, and monoterpenes were repellent to S. zeamais, except for (E)-methyl cinnamate. For C. maculatus, this effect was lower, being citral the most repellent compound. Results demonstrate the insecticidal potential of the essential oil of O. basilicum and its monoterpenes in the control of stored grain pests.

Highlights

  • Post-harvest grain weight damage caused by insect-pests ranges between 20 and 60% weight losses (CASTRO-ÁLVAREZ et al, 2015)

  • The toxicity and repellency of the essential oils of four basil cultivars and three basil hybrids and the monoterpenes linalool, citral, and (E)-methyl cinnamate were evaluated in the stored grain pests Callosobruchus maculatus and Sitophillus zeamais

  • All essential oils from cultivars, hybrids, and monoterpenes were repellent to S. zeamais, except for (E)-methyl cinnamate

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Summary

Introduction

Post-harvest grain weight damage caused by insect-pests ranges between 20 and 60% weight losses (CASTRO-ÁLVAREZ et al, 2015). Besides the direct losses due to its feeding, this insect attacks healthy grains, inside which larvae and adults feed and develop (OJO; OMOLOYE, 2012). Cowpea seed beetles are one of the most important pests of cowpea Vigna unguiculata (L.) Walp, and can attack other grains, such as Phaseolus vulgaris (L.), Vigna radiata (L.), Glycine max 32 (L.), Lens culinaris (Medikus), Pisum sativum (L.), Vicia faba (L.), Cajanus cajan (L.), and Cicer arietinum (L.). Chemicals of several toxicological classes are the most commonly used control method to combat these insects. This fact has led to several problems, such as the presence of high levels of residues in the grains and the emergence of resistant insect populations (RESTELLO et al, 2009; LU et al, 2013). The development of alternative control methods with a different mode of action from that of synthetic insecticides is imperative (COITINHO et al, 2011)

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