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Botanical insecticide, Eucalyptus snout beetle, Eucalyptus globulus, Gonipterus scutellatus, petty spurge, pichoga
Background: Gonipterus platensis (Marelli) is part of the Gonipterus scutellatus species complex which consists of three species that have spread beyond their natural ranges. Due to its high reproductive potential and a capacity for intense defoliation by both larvae and adults, G. platensis causes tree growth loss and stem deformities. The antifeeding effect and insecticide efficacy of latex from petty spurge, Euphorbia peplus L. (Euphorbiaceae), on larvae of G. platensis, were evaluated through bioassays, with a view to its integrated management.
Methods: Eucalyptus globulus leaves treated by immersion in Euphorbia peplus latex solutions were infested with five third-instar larvae, and the area consumed was determined at 24 h. The antifeeding effect of five latex solutions applied with a brush on Eucalyptus globulus leaves, using a random experimental design of six treatments and five replications, was also evaluated. Larval mortality was recorded daily and analysed by an ANOVA and Tukey’s test. The LC50 (lethal concentration to kill 50% of the individuals) was calculated by Probit analysis and Chi2 tests were performed.
Results: The ethanolic solutions of the latex caused strong antifeeding effect, with total inhibition of larval feeding at all solutions. Larval mortality increased significantly over time up to 76%, due to the effect of the ethanol latex solutions, in all solutions by day 6. The lower LC50 values were 0.049 and 0.012% w/v on days 5 and 6, respectively.
Conclusions: These results indicate that Euphorbia peplus latex is a promising bioinsecticide and a possible alternative for integrated pest management. However, further tests should be carried out.