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.
Highlights
Ants of the Atta and Acromyrmex genera (Formicidae: Myrmicinae: Attini) are the true leaf cutting-ants with their species utilizing fresh plant parts, mainly leaves, to cultivating fungus of the Leucoagaricus and Leucocoprinus genera (Agaricaceae: Leucocoprinae) (Della Lucia et al, 2014)
Leaf cutting-ants use green leaves what justifies their importance by reducing survival, growth and reproduction of plant of economic value (Zanetti et al, 2000b; Zanetti et al, 2014)
Leaf cutting-ants are the main pests in cultivated forests of the Pinus and Eucalyptus genera (Zanetti et al, 2014)
Summary
Ants of the Atta and Acromyrmex genera (Formicidae: Myrmicinae: Attini) are the true leaf cutting-ants with their species utilizing fresh plant parts, mainly leaves, to cultivating fungus of the Leucoagaricus and Leucocoprinus genera (Agaricaceae: Leucocoprinae) (Della Lucia et al, 2014). The leaf cutting-ants are one of the most significant pests in Neotropical America damaging almost all cultivated plants and causing losses to agriculture, forest and pasture plants (Zanetti et al, 2000a; Zanuncio et al, 2002). Leaf cutting-ants are the main pests in cultivated forests of the Pinus and Eucalyptus genera (Zanetti et al, 2014). Damages by leaf cutting-ants is common in forest commercial cultivation in 2005 in 3.4 million of hectares planted with eucalyptus, 1.8 million with Pinus and 326 thousand with other plant species (Pereira & Santos, 2008). The leaf cutting-ants can be controlled with different methods, but toxic baits are the most practical and efficient one (Laranjeiro et al, 1995; Zanuncio et al, 2000). Thermal fogging with plant extracts could be an alternative to these baits, but the costs of equipments with this method is much higher compared to toxic bait application (Zanetti et al, 2014)
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