AbstractThe constant search for natural insecticides in the form of extracts from many plants has received attention, and many of these extracts have been evaluated for their effectiveness as insecticides. To determine the toxic effect of six plant species Arundo donax L. (Poaceae), Brassica campestris L. (Brassicaceae), Cynodon dactylon L. (Poaceae), Hura polyandra Baill. (Euphorbiaceae), Phytollacca icosandra L. (Phytolaccaceae) and Sida acuta Burn. (Malvaceae) on Trialeurodes vaporariorum W. (Homoptera: Aleyrodidae) (adult whitefly), we evaluated the mortality rate and the lethal concentration (LC50) of the methanolic and aqueous extracts under laboratory and greenhouse conditions in a culture of Lycopersicum esculentum Mill. (Solanaceae). Analysis of Variance ANOVA and a test of comparison of means (Tukey, a = 0.05) showed a tendency of the methanolic extract in the six species towards a higher mortality rate and LC50 compared to that of the aqueous extract, both under greenhouse and laboratory conditions. The methanolic and aqueous extracts of A. donax and P. icosandra showed a higher toxicity under laboratory conditions (39.5 y 40.5%, respectively) than under greenhouse conditions (23.3 and 26.3%, respectively). The Treatments did not interfere with the tomato yield; so we are able to confirm the effectiveness of A. donax and P. icosandra extracts in the control of T. vaporariorum, which represents an ecological alternative for pest control in open field crops.
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