Seletividade do extrato hexânico de frutos de Ricinus communis L. (Euphorbiaceae) à Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae)

Abstract

The use of plant extracts is a promising alternative for the control of pest insects, due to the diversity of extracted compounds, being castor, Ricinus communis L. (Malpighiales: Euphorbiaceae) a plant that stands out in terms of its insecticidal potential, through different extracts. Generally, botanical insecticides are safer than synthetic chemical insecticides, but they can cause negative effects on the complex of natural enemies, such as the egg parasitoid Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae), widely used for the control of lepidopterans. In this context, with a bias to Integrated Pest Management (MIP) selectivity studies are fundamental for the establishment of effective and environmentally safe control strategies. Thus, the objective of this work was to evaluate the selectivity Hexanic Extract of fruits and seeds of R. communis (EHRC) over the egg parasitoid T. pretiosum, in eggs Chrysodeixis includens Walker, 1858 (Lepidoptera: Noctuidae), under laboratory conditions. For this, eggs from C. includens were immersed in the EHRC, in concentrations 0.5%, 1,0% and 2,0% in three different bioassays. 1) Preference of T. pretiosum parasitism among treated and untreated C. includens eggs - test with a choice; 2) Effect of the EHRC on T. pretiosum parasitism - test with no choice (preparasitism); 3) Selectivity of the EHRC to T. pretiosum larvae - test without choice (postparasitism). The parameters evaluated were: parasitism, emergence, sex ratio, duration of the egg-adult period and longevity. The EHRC reduced the parasitism of T. pretiosum in eggs of C. includens and presented toxicity on the immature phase of the parasitoid, being, therefore, not selective to T. pretiosum regarding the parasitism parameter. Regarding the parameters of emergency and sex ratio, the EHRC is selective, as it did not interfere with the parasitoid. As for the egg-adult period and longevity parameters, the EHRC caused some changes, however, it is inferred that such changes do not have practical results capable of harming the population in the field, and can be considered selective. Considering the potential of R. communis and T. pretiosum for pest control, additional studies with different strategies for applying the extract and releasing the parasitoid are importante.