287 - Spinosad ovicidal activity: Another tool to control Aedes aegypti - dengue vector mosquito

Abstract: The Aedes aegypti mosquito is widely distributed throughout the world, with great epidemiological importance in areas where arboviruses are transmitted. Behavior such as skip oviposition associated with survival through egg quiescence has increased the complexity of its control, especially in environments with precarious sanitary conditions. Strategies for using larvicidal and adulticidal insecticides have been carried out in Brazil since 1996 to eliminate Ae. aegypti, presenting unsatisfactory results so far. Concerning issues for this discussion are the low coverage of the species' breeding sites and the absence of insecticides capables of eliminating the mosquito in its embryonic phase. In this context, the present study evaluated the ovicidal potential of spinosad, based on some empirical field observations. Bioassays with eggs of Ae. aegypti RecL, a Laboratory colony, were carried out with concentrations (20, 30, 50, 70 and 100 mg/L) of NATULAR®NT technical powder, containing 93% of the spinosins A and D, against groups of recently laid eggs or with 24, 48 and 72 h after the start of embryogenesis. The results revealed that immediate contact with spinosad led to the unviability of the majority of eggs (80%) and that contact after 24 hours of embryogenesis dropped to < 60% even with the highest concentrations of the compound. This percentage was even lower (< 20%) when eggs were already 48 or 72 hours after oviposition. When NATULAR®EC20 was used in dosages of 10, 30 and 50 ml/10L, embryo mortality was 95% to 100% for newly laid eggs and > 90% for those at an advanced stage of embryogenesis, even at lower concentration. These responses confirm the ovicidal action of spinosad and indicate that the EC20 formulation enhanced this effect. Furthermore, the product also eliminated around 60% of females that had contact with it during oviposition, in laboratory tests.