Bioatividade de óleos essenciais sobre Euschistus heros F. (Hemiptera: Pentatomidae)

Abstract

Among the main pest soybean insects pest, stink bugs Euschistus heros (Hemipetera: Pentatomidae) stands out, which when feeding on the plant tissue causes direct and indirect damages to the plant, compromising its development and the quality of the grain. In agroecological production systems insect control is carried out using natural products such as plant-based biological insecticides such as plant extracts and oils. However, the availability of such products is limited when compared to conventional ones, which requires studies on potential plant-based insecticides. In this sense, the objective of this work was to evaluate the bioactivity of essential oils on eggs and nymphs of E. heros and to identify the compounds of the oils that present an insecticidal effect. The essential oils of pitanga (Eugenia uniflora), Guaçatonga (Caseriana sylvestris), Goiaba (Psidium guajava) and Mangerona (Origanum majorana) were used for egg testing. From the oil in natura the dilution was obtained obtaining the solution in the concentration of 2%. The application was performed by immersion technique, using six replicates (Petri dishes) with 20 eggs per bioassay in each. The evaluation was performed daily for seven days, quantifying the number of hatched nymphs. The experiment was carried out in an air conditioned environment at 27 ± 2 ° Crelative humidity 60 ± and photoperiod of 14 hours. For the test with insects third instar nymphs were used, in which the volume of 5 uL of the essential oils was applied to 3% with the aid of a micropipettor. The preparation of the experiment was carried out under the conditions described for the egg test. The design was a completely randomized design with four replicates (Petri dishes) containing 15 insects per plaque. The evaluation was performed daily until the fifteenth day, registering the number of dead insects. No effect of essential oils on E. heros eggs was observed, however, 3% E. uniflora oil has an insecticidal effect on third instar nymphs, causing an average mortality of 45% of the insects, differing significantly from the control, The other oils had no effect on the nymphs, the oil of E. uniflora has twelve different compounds in its constitution, being the majority. Aiming at the need to develop new inputs for pest control in agroecological production systems, studies with other oils and the association of control agents are necessary.