Óleos essenciais como alternativa de controle de Callosobruchus maculatus (Fabr., 1775) (Coleoptera: Chrysomelidae, Bruchinae) em grãos de feijão-caupi (Vigna unguiculata): toxicidade, efeito subletal e qualidade dos grãos

Abstract

Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae: Bruchinae) is one of the main directives of stored cowpea, causing significant losses in weight, nutritional quality and grain predictions, especially in low-technology storage systems. In search of sustainable alternatives to the use of synthetic insecticides, essential oils are highlighted as promising tools in the management of stored product directives. The present study aimed to evaluate the contact toxicity, fumigant activity and repellent effect of essential oils from Origanum vulgare L., 1753, Hyssopus officinalis L., 1753, Syzygium aromatic (L.) Merr. & L.M. Perry, 1939, and Plukenetia volubilis L., 1753 on C. maculatus adults. The bioassays were prolonged under controlled conditions of temperature, humidity and photoperiod at the Insect-Plant Interaction Laboratory at the Federal University of Grande Dourados (UFGD). In the contact toxicity test, beans treated with different concentrations of essential oils were offered to insects, therefore lethal concentrations (LC₅₀ and LC₉₅) were estimated. In fumigation tests, insects were exposed to oil vapors in airtight chambers to assess respiratory mortality. The repellent effect was determined through choice arenas, calculating the repellency index (RI). Additionally, the instantaneous population growth rate and the quality of the treated grains were evaluated. The results revealed that essential oils have different efficiency depending on their chemical composition and route of exposure. O. vulgare oil showed greater contact toxicity, with lower LC₅₀ and LC₉₅ values. H. officinalis stood out for its greatest fumigant and repellent effect, with a repellency index of less than 1. S. aromaticum showed moderate toxicity and a low repellent effect, while P. volubilis was the least efficient in all evaluations. In relation to sublethal effects, the reduction of the population growth rate in the most efficient treatments was encouraged, reducing interference in the development of the species. Regarding grain quality, no significant changes were observed in the evaluated parameters.