Proximal analysis and toxicity of extracts from young and mature leaves of the boldo tree (Peumus boldus) on elm leaf beetle (Xanthogaleruca luteola)

Abstract

A series of pests have been detected in plantations and urban trees, affecting directly the economy and recreational areas. The elm leaf beetle, Xanthogaleruca luteola Müller (Coleoptera: Chrysomelidae), is an insect pest that skeletonises the leaves of Ulmus spp., trees with a great ornamental value, which can become completely defoliated. The boldo tree (Peumus boldus Molina) is an evergreen plant endemic in Chile that contains secondary metabolites. Proximal analysis and insecticidal effects of extracts obtained from young and mature leaves with water and ethanol from P. boldus were evaluated at various concentrations on X. luteola under laboratory conditions in a completely randomized experiment considering two leaf maturity stages and solvents. Dry weight, water content, ash, and crude fiber leaf flour were significantly different between maturity stages, but the percentage of lipids and proteins were similar. Also, the 50% lethal concentration (LC50) was determined for each extract. The extracts obtained with both solvents were effective in controlling X. luteola adults in the laboratory, reaching over 50% average mortality at concentrations greater than 3.6% (w/v) in the young leaf extract and 4.0% (w/v) in the mature leaf extract. The lowest LC50 was 1.2% (w/v), obtained from the young leaf extract with ethanol after 48 h. This bioinsecticide from the leaves of P. boldus suggests an interesting opportunity for use in integrated pest management of X. luteola.