ORIGINAL PAPER Optimization and synthesis of silver nanoparticles using Isaria fumosorosea against human vector mosquitoes A. Najitha Banu & C. Balasubramanian Received: 20 June 2014 /Accepted: 23 July 2014 /Published online: 3 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract The efficacy of silver generated larvicide with the help of entomopathogenic fungi, Isaria fumosorosea (Ifr) against major vector mosquitoes Culex quinquefasciatus and Aedes aegypti. The Ifr-silver nanoparticles (AgNPs) were characterized structurally and functionally using UV-visible spectrophotometer followed by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and Fourier transform infrared (FTIR) spectra. The optimum pH (alkaline), temperature (30 °C) and agitation (150 rpm) for AgNP synthesis and its stability were confirmed through colour change. Ae. aegypti larvae (I–IV instars) were found highly susceptible to synthesized AgNPs than the larvae of Cx. quinquefasciatus. However, the mortality rate was indi- rectly proportional to the larval instar and the concentration. The lethal concentration that kills 50 % of the exposed larvae (LC 50 ) and lethal concentration that kills 90 % of the exposed larvae (LC 90 ) values of the tested concentration are 0.240, 0 0.075.337, 0.430, 0.652 and 1.219, 2.210, 2.453, 2.916; 0.065, 0.075, 0.098, 0.137 and 0.558, 0.709, 0.949, 1.278 ppm with respect to 0.03 to 1.00 ppm of Ifr-AgNPs against first, second, third and fourth instars of Cx. quinquefasciatus and Ae. aegypti, respectively. This is the first report for synthesis of AgNPs using Ifr against human vector mosquitoes. Hence, Ifr-AgNPs would be significantly used as a potent mosquito larvicide. Keywords Isaria fumosorosea . Silver nanoparticles . Toxicity . LC 50 and LC 90 Introduction One of the major public health concerns in developing coun- tries is vector-borne diseases. The genera Aedes, Anopheles and Culex adults transmit serious human diseases; viz, malar- ia, filariasis, encephalitis, dengue and recently chikungunya are the major mosquito-borne diseases in India. In the current situation of global warming and contaminated fresh water bodies, a number of mosquitoes are markedly increasing in concurrence with a high incidence of dengue fever (Halstead 2007). Mosquitoes constitute the most important single family of insects from the stand point of human health. In this regard, Aedes aegypti (Diptera: Culicidae) is the main vector of chikungunya and dengue fever (Sourisseau et al. 2007). Till 10th October 2012, 151 districts of eight states/provinces of India have been affected by chikungunya fever (Pialoux et al. 2007; Yang et al. 2009). According to WHO report of year 2009, two fifth of world population is under risk of dengue infection (WHO index) and in year 2010, 28,292 cases of infection and 108 deaths were reported in India (NVBDCP 2011). The incidence of dengue has grown dramatically around the world in recent decades over 2.5 billion people (40 % of the world’ s population) at risk from dengue. WHO currently estimates that there may be 50– 100 million dengue infections worldwide every year (WHO 2012). Dengue cases were reported in the year 2012, November 27, the total number of dengue cases in India around 35,066 and 216 deaths. The highest numbers of den- gue cases were recorded in the country for the year 2012 to 2013 till November 15, around 9,249 cases in Tamil Nadu and West Bengal 6,067 cases. Lymphatic filariasis is a serious public health problem in India, constituting one third of the infected population in the world (WHO 1997). Culex quinquefasciatus is a vector of lymphatic filariasis, which affects 120 million people world- wide, and approximately 400 million people are at risk of A. N. Banu (*) : C. Balasubramanian Department of Zoology and Microbiology, Thiagarajar College (Autonomous), Madurai, Tamil Nadu 625009, India e-mail: najirila2010@gmail.com Parasitol Res (2014) 113:3843–3851 DOI 10.1007/s00436-014-4052-0