Estudo experimental sobre a ação de larvicidas em populações de Aedes aegypti do município de Itabuna, Bahia, em condições simuladas de campo*

Abstract

Objective: to evaluate, under simulated field conditions, the efficacy of pyriproxyfen (juvenile hormone), novaluron (chitin inhibitor) and spinosad (biolarvicide) in controlling Aedes aegypti. Methods: periodic exposition of Ae. aegypti larvae collected in Itabuna, BA, Brazil, to recipients treated with larvicides and comparison of residual effect of treatment with the Rockefeller strain. Results: the inhibitory effect on adult emergence after 60 days was spinosad 89.5%, novaluron 96.5% and pyriproxifen 75.4% for Itabuna larvae, with no statistical difference (p=0.412) between treatments; spinosad and novaluron had a higher percentage of mortality in the larval stage, 98.8% and 97.9% respectively; pyriproxyfen showed higher mortality (95.1%) in the pupal stage. Conclusion: the three larvicides demonstrated similar control; however, pyriprofyxen might give a false impression of breeding ground positivity as it acts at the pupal stage, compromising the indicators of infestation that are strategic parameters for control actions.

Assessment of the Susceptibility Status of Aedes aegypti (Diptera: Culicidae) Populations to Pyriproxyfen and Malathion in a National Wide Monitoring of Insecticide Resistance in Brazil, 2017-2018.

“…These populations are likely experiencing an initial process of selection where only few individuals are resistant so far. The pyriproxyfen RR s were low, when compared to those previously reported for temephos: Itabuna reported RR 95 of 18.6 and 55.8 in 2004 and 2013, respectively; Serrinha had 254.9 in 2012 and Juazeiro do Norte showed RR 95 of 10.4 in 2003 and 17.5 in 2004 [29,3]. This regionalization should be related with differences in operational applications and quantity of insecticides used, but also with peculiarities in the genetic background of populations.…”

“…Emerging resistance to all the main classes of neurotoxic insecticide (CA s, OP s) has been detected in Ae. aegypti from Americas, Africa, and Asia [29]. The occurrence of resistance to the IGR, most recently adopted class of insecticides, reinforces the importance of using integrated tools that can contribute to reducing the need for chemical vector control, modifying the determinants of arbovirus transmission in a sustainable manner, such as environmental management and education [35].…”

“…Even if implemented, biological control must be used rationally just as it is required for chemical insecticides. Despite the believed unlike emergence of resistance to Bti due to its multiple modes of toxicity, some mechanisms of resistance to this compound were described in laboratory selected strains [29,40]. Finally, an alert should be made about the high frequency of populations with the presence of Ae.…”

Susceptibility of Aedes aegypti populations to pyriproxyfen in the Federal District of Brazil

“…In this study, the mortality of larvae from field populations ranged from 0.6 to 2.0%, and that of pupae ranged from 99 to 88%, at a 30 ng/mL dose. This can be explained by the activity of PPF during the pupal phase, when comparative studies of field simulations between the Rockefeller and Itabuna/Bahia populations are conducted, with mortality rates of 97.9 and 95.1%, respectively 39 . Conversely, the larval mortality rate o was only 2.1 and 4.9%, respectively.…”

Assessment of the susceptibility status of Aedes aegypti (Diptera: Culicidae) populations to pyriproxyfen and malathion in a national wide monitoring of insecticide resistance in Brazil, 2017-2018.

“…Those data were collected before the introduction of pyriproxyfen use suggesting cross resistance. In the case of Itabuna, Bahia State, simulated eld trials carried out in 2015 showed 100% e cacy of pyriproxyfen within 30 days after application of pyriproxyfen, however with a signi cant drop in the EI after 45 days [29]. Further investigations are required in order to better understand the related mechanisms.…”