Bioinseticidas e personalidade de colônias de Atta spp. (Formicidae: Attini): toxicidade e efeitos subletais

Abstract

Leaf-cutting ants [Hymenoptera: Formicidae: Myrmicinae: Attini: Attina] are pests of great importance in tropical agriculture and forestry due to their defoliating habits, wide distribution, and abundance. They live in symbiosis with the basidiomycete fungus Leucoagaricus gongylophorus (Basidiomycota: Agaricaceae) for over 50 million years, using fresh plant material for its cultivation. The economic importance of leaf-cutting ants arises from the billions of dollars in losses they cause to various crops, both agricultural and forestry. Currently, the main control method consists of toxic baits containing active ingredients such as sulfluramid and fipronil. However, sulfluramid has been identified as a precursor of PFOS (perfluorooctane sulfonic acid, C8HF17O3S) in the environment. In this context, botanical insecticides are considered promising as an efficient alternative for managing leaf-cutting ants. Thus, the objectives of this work were: (i) to review the main plant species and their major compounds used in alternative control methods of leaf-cutting ants through essential oils; (ii) to evaluate the insecticidal potential of the Croton grewioides (Euphorbiaceae) essential oil on Atta sexdens workers; and (iii) to conduct behavioral studies on colonies of A. sexdens and A. opaciceps. To achieve these goals, a review was carried out through scientific, technological, and molecular mapping, as well as toxicity tests with workers to determine lethal effects through lethal doses and times (LDs and LTs) and sublethal effects through behavioral and locomotion bioassays. Additionally, the tests included behavioral approaches on colonies stimulated with C. grewioides essential oil and its major compounds. In the review, seven plant families were identified as sources for essential oil extraction: Aristolochiaceae, Euphorbiaceae, Lamiaceae, Myrtaceae, Piperaceae, Verbenaceae, and Winteraceae, as well as 28 patents related to the use of essential oils against pest insects, including leaf-cutting ants. Although Brazil has the largest number of scientific publications on this topic, the number of registered patents does not follow this trend. In the toxicity bioassays, all evaluated botanical compounds were toxic and, overall, the essential oil of C. grewioides and its major compounds showed lethal and, most importantly, significant sublethal effects, such as disruption of social behaviors and high repellency to A. sexdens workers. Behavioral bioassays demonstrated that there are variations in the personality of the leaf-cutting ant species A. sexdens and A. opaciceps, as well as between colonies of each species. The results reinforce the potential of essential oils as sustainable alternatives to conventional insecticides in the management of leaf-cutting ants.