Effects of Astilbin from Dimorphandra mollis (Fabaceae) Flowers and Brazilian Plant Extracts on Sitophilus zeamais (Coleoptera: Curculionidae)

Botanical extracts can be an alternative to synthetic insecticides for pest management, owing to their efficiency and environmental safety. The lethal times (LT₅₀ and LT₉₀), loss of grain weight, and repellence of Sitophilus zeamais (Coleoptera: Curculionidae) were evaluated when extracts from 5 plant species from the Brazilian Cerrado biome [Adenocalymma nodosum (Bignoniaceae) leaves, astilbin from Dimorphandra mollis (Fabaceae) flowers, Psychotria prunifolia (Rubiaceae) leaves, Senna obtusifolia (Fabaceae) leaves, and Tithonia diversifolia (Asteraceae) flowers] were applied to a surface and to food. The weevils exposed to a surface treated with extracts from T. diversifolia flowers (106.43 h) and P. prunifolia leaves (119.68 h) at 2% (m.v⁻¹) presented the lowest LT₅₀ and LT₉₀ values, respectively. Corn grains treated with the extract from P. prunifolia leaves at 2% (w.w⁻¹) exhibited fastest mortality of S. zeamais individuals with lower values of LT₅₀ and LT₉₀ than the other treatments. All the botanical extracts repelled S. zeamais after 30 min of application; however, the extracts from S. obtusifolia leaves, P. prunifolia leaves, and T. diversifolia flowers at 2% (m.v⁻¹) repelled this insect after 6 min. Moreover, at 90 and 120 min after the beginning of the experiment, the extracts from P. prunifolia leaves and T. diversifolia flowers repelled the adult weevils. The extracts from A. nodosum leaves, P. prunifolia leaves, and T. diversifolia flowers applied to corn grains showed class III repellency according to the Preference Index for S. zeamais and less grain weight loss, when compared with astilbin from D. mollis flowers and S. obtusifolia leaves. Therefore, it was concluded that the extracts from T. diversifolia flowers and P. prunifolia leaves were the most promising in controlling S. zeamais, with the potential for application in programs for the integrated management of this pest.