189 - Spinosad adulticidal activity by contact and ingestion in toxic sugar bait: another potential approach to control Aedes aegypti.

Abstract: Aedes aegypti is a species of mosquito with high vector capacity for the transmission of arboviruses such as Dengue, Zika and Chikungunya. Strategies aimed at eliminating adult mosquitoes in Brazil, since 1996, have been restricted to the perifocal or spatial (ultra-low volume) application of chemical insecticides. These products are applied every two weeks at strategic points, such as cemetery, tire repair shop and junkyard, as a “shock” treatment, to eliminate mosquitoes in the first few days after application. This constant use can cause a selection pressure for resistance in the field, which makes rotation between products necessary. Although spinosad is considered an excellent biological product with larvicidal action, we raise here the possibility of its adulticidal effect, through direct contact and/or ingestion in toxic sugar baits, for the control of Ae. aegypti. Bioassays with Ae. aegypti RecL, a laboratory colony, were carried out with different concentrations (0.5, 1.0, 2.0 and 5.0%) of NATULAR®NT technical powder (93% of the spinosins A and D) in a 20% sugar suspension, against groups of recently emerged males and females. The results revealed that for the lowest concentrations, total mortality occurred within four days, while with 2% and 5% it occurred two days after ingestion. On the other hand, the immediate contact of adult mosquitoes with the impregnated filter paper with aqueous suspensions of 10, 30 and 50 ml/10L of NATULAR®EC20 led to total mortality of males and females exposed within 24 h, despite the concentration of 50 ml/10L already eliminated all of them with just 30 min of exposure. These results point out a new effect of this biological product, which could lead to its indication for interventions at strategic points, acting on the joint elimination of larvae and adult mosquitoes, in a single form of application.