Effects of feeding amount on the growth and development of tobacco cutworm larvae

Effects of controlled feeding on the growth and development of tobacco cutworm larvae (Spodoptera litura) were studied.In contrast with azadirachtin,the growth and development of tobacco cutworm were measured under natural condition.The 3rd instar larvae of tobacco cutworm were treated with controlled feeding.The results showed that the fewer was the feeding amount,the greater the effect of growth inhibition was,the longer the duration of development was and the higher the mortality was.But the pupation rate and eclosion rate were not obviously affected.The 3rd instar larvae of tobacco cutworm were treated with azadirachtin at different concentration.Results showed that the higher the concentration of azadirachtin was,the greater the effect of growth inhibition was.The duration of larvae treated with azadirachtin became longer and the mortality was higher.It was similar with the results of controlled feeding.Moreover, the pupation rate and eclosion rate of larvae treated with azadirachtin were obviously lower, and it did not tally with the results of controlled feeding.The probable reason was that azadirachtin had inhibition activity of growth and development in addition to antifeeding activity.