Toxicity of plant extracts from Bahia, Brazil, to Atta sexdens sexdens workers (Hymenoptera: Formicidae)

Abstract

The aim of this study was to evaluate the toxicity of extracts of Aspidosperma spruceanum Benth ex. Mull Arg. (leaf and bark), Casearia arborea (Rich.) Urb. (leaf and branch), Casearia sylvestris Sw. (leaf and bark), Erythroxylum affine A.St.-Hil. (leaf and branch), Esenbeckia grandiflora Mart. (leaf and bark), Ocotea brasiliensis Coe-Teix (bark and branch), Simarouba amara Aubl. (bark), Tabernaemontana bracteolaris Mart. ex Müll.Arg.  (leaf, bark and branch) and Zanthoxylum rhoifolium Lam. (leaf and branch) plant species, collected in the state of Bahia, Brazil, to workers of Atta sexdens L. cutting-ants. The toxicity of extracts was assessed through tests of ingestion and contact, with topical application on thorax of ants and through addition of extracts in diet, respectively. Data of topical application were submitted to analysis of variance and to the Tukey test while data from ingestion were compared by survival curves using the statistical test ¨log rank¨. Through contact, the extracts of leaf and branch of Z. rhoifolium and of bark of S. amara were the most toxic ones. Through ingestion, four extracts were toxic and were characterized as of delayed action, with the extract of Z. rhoifolium branch presenting the slowest action (S50= 10 days). This characteristic is crucial to its possible use in toxic baits. The extracts of leaf and branch of Z. rhoifolium were the only ones that presented toxicity through contact and ingestion.