CONTROL OF KHAPRA BEETLE BY LEAF EXTRACT OF Melia azedarach AND IDENTIFICATION OF POSSIBLE INSECTICIDAL COMPOUNDS THROUGH GC-MS ANALYSIS
The leaf extract of Melia azedarach was obtained by soaking plant material in ethanol for one week and its toxic effect was assessed on the third instar larvae of Trogoderma granarium. Four concentrations (2, 4, 6 and 8 µL mL-1 acetone) were applied through contact method in Petri plates. Mortality was recorded after 12, 24 and 36 h. All the concentrations showed toxic effects against the larvae to variable extents. The highest mortality i.e. 72% was recorded at 8 µL mL-1 acetone concentration after 36 h incubation period. At the same concentration, the mortality was 61.67% and 48.34% after 24 and 12 h, respectively. Minimum mortality (23.33%) was observed at 2 µL mL -1 acetone concentration after 12 h. GC-MS analysis of ethanolic leaf extract of parthenium revealed the phytol as the predominant compound with 72.25% peak area. Other compounds were 2(4H)-benzofuranone, 5,6,7,7a-tetrahydro-4,4,7a-trimethyl- (6.30%), 1-(3,6,6-trimethyl-1,6,7,7a-tetrahydrocyclopenta[c]pyran-1-yl)ethanone (6.11%), methyl stearate (4.60%), (+/-)-phytone (4.38%), hexadecanoic acid, methyl ester (3.24%), and hexadecanoic acid, ethyl ester (3.12%). It is concluded that an 8 µL mL-1 acetone concentration of leaf extract of M. azedarach can kill up to 72% larvae of T. granarium in 36 hours.