Toxicidade de óleos essenciais e nanoemulsões de lamiáceas e poáceas para Spodoptera frugiperda e Chrysodeixis includens e para seus parasitoides Telenomus remus e Trichogramma pretiosum

Abstract

The intensification of agricultural systems and the extensive use of synthetic insecticides have increased the challenges associated with the management of Spodoptera frugiperda and Chrysodeixis includens. In addition to selecting resistant populations of these pests, these compounds may adversely affect non-target organisms and negatively impact the environment, reinforcing the need for new sustainable management strategies compatible with natural enemies for incorporation into management programs targeting these noctuid pests. Essential oils (EOs) and botanical nanoformulations have emerged as promising alternatives due to their high chemical diversity, multiple modes of action, and potential compatibility with natural enemies. This dissertation comprises six manuscripts investigating the insecticidal potential of EOs and nanoemulsions derived from species of the families Lamiaceae and Poaceae against S. frugiperda and C. includens, as well as their selectivity toward the egg parasitoids Telenomus remus and Trichogramma pretiosum. Initially, the toxicity of EOs from Origanum vulgare, Cymbopogon flexuosus, Cymbopogon winterianus, and Ocimum basilicum, as well as their major constituents, was evaluated against S. frugiperda and C. includens through topical application and ingestion. In both species, toxicity varied according to the chemical composition of the EOs, the toxicity of their major constituents, and the route of exposure, with the major constituents frequently exhibiting greater toxicity than their corresponding EOs. Subsequently, the lethal and sublethal effects of the EOs on the biological, reproductive, and demographic parameters of both noctuid species were investigated using life table analyses. Sublethal concentrations impaired development, survival, fecundity, longevity, and population parameters, thereby reducing the population growth of both species. In C. includens, the EOs of O. basilicum and C. flexuosus altered population dynamics, whereas morphological changes observed in adults treated with O. basilicum provided evidence of sublethal effects on insect development. Subsequently, the toxicity of EOs and botanical nanoemulsions against S. frugiperda and their selectivity toward the egg parasitoids T. remus and T. pretiosum were evaluated. The nanoemulsions enhanced the insecticidal activity of the EOs against S. frugiperda larvae while exhibiting low toxicity toward the parasitoids during their immature development within host eggs. In contrast, adult females of both parasitoid species were highly susceptible following direct exposure. Additionally, the EO of O. basilicum induced transgenerational effects on T. remus, maintaining partial compatibility during its immature developmental stages while also exhibiting high toxicity against S. frugiperda. Overall, the 9 results demonstrated that EOs and their nanoemulsions have considerable potential for the sustainable management of these lepidopteran pests by combining insecticidal activity with selectivity that depends on the exposure stage of egg parasitoids. Nevertheless, additional semifield and field studies are still required to validate their efficacy and potential incorporation into integrated management programs for these lepidopteran pests.