Effects of chitosan on feeding and growth of third and fifth instars of the cotton bollworm,Helicoverpa armigera

The cotton bollworm, Helicoverpa armigera (Lep.;Noctuidae) is a serious pest of 181 plant species. The pest is damaging to over 70 crops due to its polyphagous nature. Chitosan is one of the biocompatible compounds that has been recently considered for its insecticidal, antifeedant and anti-growth effects. In this study, nutritional effects of chitosan (Manufacturing company Sigma) were studied under laboratory conditions (27±2°C, 70±5% R.H. and L 16: D 8) on third and fifth instars of this pest. Five concentrations 2.5, 4, 6, 8 and 10 g/kg of diet were investigated in three replications. In the third instars after two days of feeding, growth inhibition was at least 21.74% and maximum 30.16%, and rates of growth stimulation were at least 2.42% and at most 9.25%. Also, the inhibitory and stimulatory levels of feeding were varied from 4.59-11.56% and 3.24-14.03%, respectively. Generally, the effect of chitosan on third instars was growth inhibition and feeding stimulation. In the case of the fifth instars after two days, growth inhibition was at least 3.86% and maximum 21.68%, and rates of growth stimulation were at least 6.46% and at most 54.95%. Also the inhibitory and stimulatory levels of feeding 4.27-10.09% and 16.26-45.17%, respectively. In general, the effect of chitosan on fifth instars was growth and feeding stimulation. The overall conclusion is that the effects of chitosan on larvae of the third and fifth instars, depending on the concentration and age of larvae, can be as growth inhibition or stimulation and nutrition inhibition or stimulation.

کلیدواژه ها:

Biopolymer ، Feeding inhibition ، Growth inhibition ، Feeding stimulation ، Growth stimulation