Insecticidal Properties of Peumus boldus Molina Powder Used Alone and Mixed with Lime Against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Gabriel Bustos-Figueroa1, Francisco Osses-Ruiz1, Gonzalo Silva-Aguayo1* Maritza Tapia-Vargas1, Ruperto Hepp-Gallo1, and J. Concepción Rodríguez-Maciel2

The insecticidal properties of boldus (Peumus boldus Molina) powder used alone and mixed with lime against adults of maize weevil (Sitophilus zeamais Motschulsky) were evaluated under laboratory conditions. Additionally, aeration effects (presence or absence) and temperature (room temperature vs. 3 ºC) on insecticidal properties were studied over time. A mortality rate of 100% was observed at 20 g kg-1 (w/w) of P. boldus powder when used alone and mixed with lime in proportions of 50:50, 60:40, and 80:20. The 50% lethal concentration (LC50) for all treatments was < 5 g kg-1, while LC90 was 11 g kg-1. Mixing corn grains with different insecticidal treatments did not affect maize germination. Temperature and aeration did not influence mortality of maize weevil adults. When the boldus powder was mixed with the infested maize 24 h before grinding, the toxicity to the parental adults and emergence of F1 adults with respect to the untreated control was 100 and 0%, respectively. The results were not satisfactory when boldus powder was stored during 30, 60, and 90 d and then mixed with the infested maize. Boldus foliage toxicity was high 24 h after grinding, but decreased significantly over time.

Key words: Boldus, maize weevil, stored corn

1 Universidad de Concepción, Facultad de Agronomía, Av. Vicente Méndez 595. Casilla 537, Chillán, Chile. *Corresponding author (gosilva@udec.cl)
2 Colegio de Postgraduados, Programa de Entomología y Acarología, km 36,5 Carretera México-Texcoco. PO Box 56230, Montecillo, Texcoco, Estado de México, México.
Deceased September 2007.