Efeito de concentração subletal de mastruz Dysphania ambrosioides (L.) sobre o ciclo de vida de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Abstract

The practices commonly used to control the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) are based on synthetic insecticides and the use of genetically modified plants, however there are reports of control failures resulting from the selection of resistant populations and adverse effects on non-target organisms. As a result, essential oils (EOs) have been studied to control this insect. Among the species that produce substances that have insecticidal activity, we can mention Dysphania ambrosioides (syn=Chenopodium ambrosioides) (L.) Mosyakin & Clemants, popularly known as mastruz. However, studies aiming to evaluate the bioactivity of D. ambrosioides towards S. frugiperda are scarce to date. Thus, this work aimed to evaluate the bioactivity of different concentrations of D. ambrosioides EO on the S. frugiperda life cycle, through the construction of a life and fertility table under laboratory conditions. The EO of D. ambrosioides had its insecticidal activity evaluated against S. frugiperda, in an ingestion test. Thus, the different concentrations of EO were solubilized in a 1% aqueous solution of Tween 80 (10 mL) and incorporated into an artificial diet (100 mL). The EOs were incorporated into an artificial diet at concentrations of 0.5; 0.7; 1 and 2 mg of EO/mL of diet. The EO of D. ambrosioides (0.5 mg of EO/mL of diet) prolonged the development of caterpillars in the 3rd and 6th instars, in addition to increasing the total life cycle. Treatment in the young phase caused physiological disturbances, evidenced by an increase in the pre-oviposition period of adults. For concentrations of 0.7, 1 and 2 mg of EO/mL in the diet, it was not possible to construct a life and fertility table due to high mortality, proving its toxicity to S. frugiperda.