Research Article Received: 11 December 2015 Revised: 15 April 2016 Accepted article published: 13 May 2016 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/ps.4315 Not in my backyard: effectiveness of outdoor residual spraying from hand-held sprayers against the mosquito Aedes albopictus in Rome, Italy Mattia Manica, a,b Pietro Cobre, a Roberto Rosà b and Beniamino Caputo a* Abstract BACKGROUND: WHO guidelines state that adulticide interventions are recommended only in case of disease outbreak. However, peridomestic sprayings are carried out routinely to reduce Aedes albopictus (Skuse) nuisance, at least in Italy. Failing to keep low adult abundance over time triggers the need for further applications. The aim of the study was to investigate the effectiveness of a common control strategy routinely performed by citizens in highly infested urban sites inside the metropolitan city of Rome using a freely purchasable pyrethroid and a hand-held sprayer. Moreover, the effectiveness evaluated in three field experiments was compared with that achieved by blending the pyrethroid with a new carbon-based liquid additive. RESULTS: An 86% post-treatment reduction in Ae. albopictus abundance was observed in gravid and host-seeking females, while the population recovery time was 10 days. Blending the insecticide with the additive lengthened mosquito recovery time to over 14 days. CONCLUSION: Peridomestic sprayings largely reduce mosquito populations immediately after treatment but fail to keep low mosquito abundance for a longer period, partially explaining the uncontrolled repetitions of treatments. An optimal control application could benefit from research in the field of additives to improve mosquito abatement and the performance of pyrethroids over time. © 2016 Society of Chemical Industry Supporting information may be found in the online version of this article. Keywords: Aedes mosquito; vector control; mosquito nuisance; vector reduction; insecticide sprayings 1 INTRODUCTION Mosquitoes are nuisance pests and potential human disease vec- tors. Nuisance vector control aims to improve the life quality of people by reducing the nuisance level and preventing or control- ling mosquito-borne diseases. 1 In the multidisciplinary practice of mosquito control, numerous methods have been developed 2 – 4 to achieve these objectives. Among others, surveillance and con- ventional control methods targeting larval populations, along with social awareness and public education, are essential. 5 – 8 Mean- while, alternative control methods are being developed. 9,10 In vec- tor control, the major concern is to maintain mosquito populations under a threshold at which disease transmission is unlikely. 11,12 When larval control does not suffice, control measures targeting adult populations are needed in order to reduce the risk of trans- mission of arboviral diseases. 13,14 Nuisance control faces similar concerns in maintaining mosquito populations under a tolerance threshold. However, the level of infestation above which control measures (and the type of measures) are justifiable has not yet been established, 3,4 despite considerable efforts to assess the pub- lic tolerance of mosquito biting. 15 In a study carried out in New Jersey, citizens reported being affected by Aedes albopictus in their social life and outdoor activities. 16 Another study in Wisconsin showed that they were more willing to pay for intervention to reduce mosquito nuisance rather than to limit the risk of disease transmission. 17 Invasive mosquitoes such as Ae. albopictus are of major concern and nuisance in people’s daily life not only because of the increased risk of the arrival and spread of arboviruses such as dengue and chikunguya 18,19 but also because of the numerous bites 15,20 result- ing from their daytime feeding behaviour. 12 Therefore, the burden of high adult mosquito density on human host cannot be ignored even in areas of low or near-zero epidemic risk. Chemical spray treatments provide a rapid method to reduce adult populations. 21,22 In its broadest sense, the term ‘spray treat- ments’ refers to various forms of intervention carried out with ∗ Correspondence to: B Caputo, Department of Public Health and Infectious Diseases, University of Rome ‘La Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy. E-mail: beniamino.caputo@uniroma1.it a Department of Public Health and Infectious Diseases, University of Rome ‘La Sapienza’, Rome, Italy b Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all’Adige, Trento, Italy Pest Manag Sci (2016) www.soci.org © 2016 Society of Chemical Industry