Toxicidade de óleos essenciais para Spodoptera frugiperda (Lepidoptera: Noctuidae) e Tuta absoluta (Lepidoptera: Gelechiidae) e seletividade para Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

Abstract

Tuta absoluta (Meyrick, 1971) (Lepidoptera: Gelechiidae) and Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuide) are important arthropod pests which cause great losses in different agricultural crops. These insects present rapid dispersal, difficult control and resistance to the main synthetic insecticides. In this way, researchers with essential oils (EO) are important for the development of new insecticides. The objective was to evaluate the insecticidal activity of the EO and the major compounds of Eugenia caryophyllus (Myrtaceae) and Foeniculum vulgare var. dulce (Apiaceae) against S. frugiperda and the physiological selectivity for the natural enemy Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). In addition, in the second manuscript, the effects of the EOs of Melaleuca alternifolia (Myrtaceae) e Eucalyptus staigeriana (Myrtaceae) were evaluated against T. absoluta. The EO and major compounds were solubilized in acetone and applied to the back of the caterpillars using a microsyringe. The EO of E. caryophyllus and F. vulgare were toxic to S. frugiperda. Specifically, a negative effect was observed on the duration of the larval stage, fecundity and on the demographic parameters of the life table of S. frugiperda. Through chromatographic analysis was verified six compounds in E.caryophyllus, the major ones being eugenol (76.2%) and (E)-caryophyllene (19.9%). F. vulgare var. dulce showed 11 constituents, being (E)-anethole the most abundant and responsible for the insecticidal activity for S. frugiperda. Only the EO and the majorities of E. caryophyllus caused toxicity to the natural enemy. The EO of F. vulgare var. dulce and the major (E)-anethole were selective for T. pretiosum in the egg-larva period and in the pupal stage. Regarding the results obtained in the second manuscript, the EO of M. alternifolia (LD50 = 76.5 μg/caterpillar) and E. staigeriana (LD50 = 78.5 μg/caterpillar) were toxic to T. absoluta in topical application. The two plant species affected the duration of the pupal stage, longevity, the intrinsic rate of increase, the finite rate of increase and the net reproductive rate of T. absoluta. The EO were submitted to chromatographic analysis. M. alternifolia contained 19 compounds, the major ones being 4-terpineol (42.2%), γ-terpinene (22.1%) and α-terpinene (10.4%). While the species E. staigeriana had 25 constituents, with limonene (27.3%), geranial (13.8%) and neral (9.9%) being the majority compounds. The obtained results demonstrate the insecticidal potential of the EO and majorities aiming at the control of S. frugiperda and T. absoluta.