Use of Essential Oils and α-Pinene as Insecticides against Sitophilus zeamais and Their Effects on Maize Seed Germination
Rodrigo de Carvalho Brito, Luiz Evaldo de Moura Pádua, Leticia Rodrigues da Silva, Marcus Eugênio Oliveira Briozo, Paulo Roberto Ramalho Silva, Luzineide Fernandes de Carvalho, Kamilla de Andrade Dutra, Daniela Maria do Amaral Ferraz Navarro, Douglas Rafael e Silva Barbosa, Mariano Oscar Aníbal Ibañez Rojas, Giovana Lopes da Silva, Mariana Oliveira Breda, Gutierres Nelson Silva, Tadeu Barbosa Martins Silva, Erlen Keila Cândido e Silva, Solange Maria de França
Abstract
This study aimed to assess the efficiency of the use of α-pinene and essential oils of Gaultheria procumbens, Juniperus communis, Protium heptaphyllum, and Protium pallidum in treating corn seeds (Zea mays) under storage conditions for the management of Sitophilus zeamais. Contact toxicity, fumigation, repellency, persistence, and residual effects of the targeted essential oil and phytocompound on germination were performed. G. procumbens oil, high in methyl salicylate (96%), was the most toxic in contact tests, with an LC50 of 26.83 µL/20 g. P. heptaphyllum oil, containing 40.1% limonene, was the second most toxic with an LC50 of 45.78 μL/20 g. When test separately, α-pinene was more toxic than J. communis oil, which has 67% α-pinene. P. pallidum oil, with 31.17% o-cimene, also showed toxicity. In fumigation tests, the toxicity order was G. procumbens ≥ P. heptaphyllum > α-pinene > J. communis > P. pallidum. All products were repellent. G. procumbens had the longest persistence (71 days), while J. communis and α-pinene had shorter persistence. J. communis oil and α-pinene did not affect corn seed germination or vigor. The findings are crucial for managing S. zeamais in stored maize and determining the appropriate use of natural insecticides without affecting their ability to germinate and grow.