TOXICITY AND REPELLENCY OF BOTANICAL INSECTICIDES TO THE ELM LEAF BEETLE, Xanthogaleruca luteola, IN THE LABORATORY

Abstract

The toxicity and repellency of the botanical insecticides Biomilbe, Biobug, Garlic Barrier, and Bugitol to the elm leaf beetle, Xanthogaleruca luteola Müller (Coleoptera: Chrysomelidae), were evaluated in the laboratory during 2008-2009. Elm leaf beetles were collected from elm trees (Ulmus sp., Ulmaceae) in Parque O`Higgins, Santiago, Chile. The products were applied at four concentrations each in a Potter tower; a control treatment only with water was also included. Toxicity by ingestion was evaluated after spraying the insecticides on leaves, which were given as food to larvae and adults after 20 min. Contact effects were determined after direct application of these products onto X. luteola specimens. In addition, their repellency on treated leaves was compared on trays with other leaves treated only with water. The toxicity tests were set in a completely randomized statistical design, with four insecticides plus the control treatment and four replicates. The experiment unit was a Petri dish with 20 individuals. Mortality was evaluated after 24 h of direct spray, and after 1 and 24 h when applied by leaf immersion. The mortality obtained was subjected to ANOVA and mean separation tests. For the repellency test, the percentages of larvae, on both treated and untreated leaves, were compared. Mortality levels were very low. The highest mortality was obtained with Bugitol at 4%, recording 37.5% larval mortality. The repellency bioassay revealed marked effects on the leaves treated with Biomilbe and Biobug, while larvae concentrated on the leaves treated only with water.