The bioefficacy of crude extracts of Azadirachta indica (Meliaceae) on the survival and development of myiasis-causing larvae of Chrysomya bezziana (Diptera: Calliphoridae)

Myiasis is a type of parasitosis originating from the invasion of tissues of live humans and other vertebrates by dipteran larvae. The Old World screwworm fly—Chrysomya bezziana—is known worldwide in the tropical regions for causing myiasis among man and domestic animals, thereby leading to health hazards and severe economic losses to the dairy farmers. Management techniques for controlling populations of the fly are needed to minimize these losses. Plant-derived materials have been increasingly evaluated these days in controlling the insects of medical and veterinary importance. This study evaluated the efficacy of crude extracts of the plant neem, Azadirachta indica, against C. bezziana. The dried leaves of the plant were extracted successively with four different solvents viz. petroleum ether, chloroform, ethyl acetate and methanol and were evaluated against the third instar larvae of C. bezziana using dipping method and thin film application technique. In the dipping method, larvae were dipped in four different concentrations of plant extracts for 30 s, whereas in the thin film application, they were exposed to a thin film of plant extracts. The results showed that all the extracts had toxic effect on the larvae in both the techniques. In the dipping method, the highest mortalities were recorded in methanol extract followed by chloroform, petroleum ether and ethyl acetate extracts with LC50 values 1.07 g/100 ml, 1.7 g/100 ml, 3.39 g/100 ml and 4.9 g/100 ml, respectively. In the thin film application method, methanol extract showed the highest mortalities followed by chloroform, ethyl acetate and petroleum ether with LC50 values 0.4 mg/cm2, 0.6 mg/cm2, 2.1 mg/cm2 and 2.5 mg/cm2. It is concluded that the crude extracts of A. indica can be used in controlling the larvae of C. bezziana by using the dipping as well as thin film application technique.