Effect of emulsion size and shelf life of azadirachtin A on the bioefficacy of neem (Azadirachta indica A. Juss) emulsifiable concentrates.
In a study of 33 recipes of neem oil based emulsifiable concentrates, the specific surface area of the emulsions and cream plus oil layer separation in emulsions at 24 h revealed a correlation of -0.6874 between them and correlations of -0.8940 and 0.6972, respectively, with bioefficacy (LC(50)) against the 3-day-old second-instar larvae of the Bihar hairy caterpillar, Spilosoma obliqua Walker. Nearly 96-99% of azadirachtin A in emulsifiable concentrates (aza-A content = 617.93-1149.65 ppm) degraded during the heat stability test at 54 +/- 1 degrees C for 14 days with half-lives ranging between 1.84 and 4.53 days. The LC(50) values against S. obliqua were, however, statistically at par in both the pre- and the post-heat-treated samples, suggesting a similar effect of azadirachtin A and its degradation products on the bioactivity. The half-life of azadirachtin A could be enhanced by storing the concentrates at lower temperatures. A low pH of the formulation solvent did not check the degradation of azadirachtin A, as reported with aqueous solutions in the literature.
Kumar
L
L
Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi.
Parmar
B S
BS
D004655:Emulsions; D005989:Glycerides / Q000737:chemistry* / Q000494:pharmacology; D007306:Insecticides / Q000737:chemistry* / Q000494:pharmacology; D036701:Limonins; D010316:Particle Size; D013729:Terpenes / Q000737:chemistry* / Q000494:pharmacology; D014315:Triterpenes / Q000737:chemistry* / Q000494:pharmacology
D004655:Emulsions; D005989:Glycerides; D007306:Insecticides; D036701:Limonins; D013729:Terpenes; D014315:Triterpenes; C002443:neem oil; C010329:azadirachtin