Bioactivity of normal and UV exposed azadirachtins A, B and H against the root-knot nematode, Meloidogyne incognita

Azadirachtins A, B and H showed LD50 of 460.7, 125.8 and 229.4 ppm, respectively against the second stage juveniles of root-knot nematode, Meloidgyne incognita. On exposure to UV light, 32 times loss in the nematicidal activity of Aza-A, 14.6 times in Aza-B and 66.5 times in Aza-H, was observed. Aza-A was the most sensitive to hydrolysis with only 17% of the initial content remaining in the aqueous nematode culture medium after 48 h. In contrast, 86 to 87% of azadirachtins B and H was found after this period. The nematode mortality correlated significantly with period of incubation and azadirachtin content of the medium. Aza-B showed the maximum nematicidal activity against M. incognita and was stable against both hydrolytic and photodegradation.