Demographic changes in Helicoverpa armigera after exposure to neemazal (1% EC azadirachtin)

We estimated the effect of 5, 10, 15 and 20 mg l(-1) of neemazal (1% EC azadirachtin) on life table parameters of Helicovema armigera (Hubner) developing on chickpea (Cicer arietinum L.). The effects were assessed on the survivals emerged from 6th instar larvae that had ingested neemazal-treated chickpea pods. Survivorship (I) and expectancy of life (e(x)) were highest with the commencement of age (egg) and decreased gradually with the advancement of age with all the concentrations of neemazal including unexposed cohort. All the eggs hatched in the unexposed group while highest numbers of unhatched eggs (10%) were recorded with 20 mg l(-1). Mortality of 1st instars was higher at 20 and 15 mg l(-1) than that of other concentration tested. Potential fecundity (pf) was reduced in concentration dependent manner and was lowest with 20 mg l(-1) (418 eggs/female/generation) and highest in control (898 eggs/female/generation). Net reproductive rate (R-0) was significantly reduced with the increase in concentration of neemazal. The intrinsic (r(m)) and finite rate of increase (lambda) were significantly decreased at 20 mg l(-1) than that of unexposed population. The mean generation time (TO was prolonged at 20 mg l(-1) and significantly differed with non-treated individuals. Development of immature stages was prolonged to 38 days with 20 mg l(-1) while reduced to 32 days with 15 mg l(-1) of neemazal as compared to 37 days in untreated individuals. Doubling time (DT) was significantly extended to 5.02 days with 20 mg l(-1) as compared to 3.84 days in the non exposed ones. (C) 2013 Elsevier Ltd. All rights reserved.