Larvicidal effect of extracellular extracts of Trichoderma longibrachiatum and Trichoderma viride against Aedes aegypti

Abstract

Aedes aegypti is a potential vector for transmitting dreadful diseases such as yellow fever, ZIKA, dengue and chikungunya, leading to global health problems. However, there is no warranted controlling method for these diseases other than controlling the vector. Apart from destroying breeding sites, use of larvicides is also important in larval control of the vector. Synthetic chemical insecticides, which dominate mosquito control programmes, are hazardous and exert unwarranted toxicity on non-targeted organisms, and lead to develop physiological resistance in target insects. Therefore, environmentally friendly, fungal mediated insecticides have been a priority at present. In current study, larvicidal effect of extra cellular fungal extracts of Trichoderma longibrachiatum and Trichoderma viride against 3rd instar larvae of Ae. aegypti was investigated. The fungi were grown in Richard’s broth medium containing glucose, agar, potassium nitrate, potassium dihydrogen phosphate, magnesium sulphate and ferric chloride. Eighteen different test concentrations of extracellular fungal filtrates, in a range from 0.625gL-1to 175gL-1, were prepared and batches of 25 number of laboratory reared 3rd instar larvae of Ae. aegypti were exposed to each test concentration separately with three replicates. Control bioassays were conducted with distilled water and larval mortality was recorded after 24 and 48 hour exposure periods. Results revealed that extracellular extracts of T. viride exhibited high larvicidal activity against Ae. aegypti larvae compared to the larvicidal activity of T. longibrachiatum. LC50 values for 3rd instar larvae of Ae. aegypti at 24 hours to the extracellular extracts of T. viride and T. longibrachiatum were 99.92 gL-1 and 114.98 gL-1respectively whereas LC50 values at 48 hours of exposure to the extracellular extracts of T. viride and T. longibrachiatum were 92.46 gL-1 and 108.71 gL-1 respectively. This study concludes that extracellular fungal extracts of T. longibrachiatum and T. viride can act as potential larvicides against Ae. aegypti and they can be used as alternatives for hazardous synthetic insecticides.