Growth inhibitory and antifeedant effect of azadirachtin-rich formulations on cotton bollworm (Helicoverpa armigera)

Abstract

Diet-incorporation bioassays were carried out during 1999-2000 to evaluate effects of azadirachtin-rich fractions (Achook, az. 1 500 ppm, Neemazal, az. 50 000 ppm and Neem Jeevan Triguard, az. 60 000 ppm) against cotton bollworm (Helicoverpa armigera Hubner). The larval mortality increased in a dose-dependent manner with the LC₅₀ of 0.612, 0.064 and 0.027% for Achook, Neemazal and Triguard respectively. At lower doses of azadirachtin, inhibition and disruption of moulting was observed, however, larval-pupal intermediates or abnormal pupae were commonly found in all the 3 neem or margosa (Azadirachta indica A. Juss.) formulations tested. The lower concentration 0.075% Neemazal and 0.05% Triguard resulted in 8.0 and 14.6% malformed adults, whereas their percentage decreased with an increase in concentration of neem. It showed that larvae treated with azadirachtin-rich fractions did not develop further stages or if developed into adults, died during eclosion or showed frizzled or curled wings of cotton bollworm.