Vacuum packed and shelf life of a grain protector based on powder of Peumus boldus Molina foliage and lime against Sitophilus zeamais Motschulsky

Paulina Rivera1, Gonzalo Silva1*, Ines Figueroa1, Maritza Tapia1, J. Concepcion Rodriguez2
The maize weevil (Sitophilus zeamais Motschulsky, Coleoptera: Curculionidae) is a key pest of stored grain maize. As an ecological pest control alternative, the use of botanical insecticides, such as powder from boldus (Peumus boldus Molina) foliage singly or mixed with lime, has been evaluated. Unfortunately, its shelf life is very short and does not exceed 15 d. The effectiveness of vacuum storage on insecticidal properties of a natural grain protector produced with boldus powder:lime at proportions of 50:50 and 60:40 against adults of S. zeamais was assessed under laboratory conditions. Treatments were evaluated at 1% and 2% (w/w) for 150 d of storage. All treatments based on boldus powder kept the level of mortality by contact activity over 80% at 150 d of storage. The highest toxicity, as a fumigant, was observed in treatments 50:50 at 2% and 60:40 at 1% and 2% with mortality over 60%. The grain weight loss was less than 1% and seed germination was not affected. With the exception of 0:100 at 2% without vacuum storage, all treatments were repellent to S. zeamais. Vacuum storage extended shelf life of the grain protector for 150 d.
Keywords: Botanical insecticides, contact toxicity, fumigant, maize weevil, repellent.
1Universidad de Concepción, Facultad de Agronomía, Av. Vicente Méndez 595, Chillán, Chile. *Corresponding author (gosilva@udec.cl).
2Colegio de Postgraduados, Campus Montecillo, km 36,5 Carretera México-Texcoco, Montecillo, Estado de México, México.