Effect of vacuum storage on shelf life of a grain protector based on Peumus boldus molina foliage powder and lime against Sitophilus zeamais motschulsky

Abstract

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.