the effect of some pesticides and plant extracts on functional response of chrysoperla carnea (stephens) to different densities of agonoscena pistaciae

functional response in natural enemies is affected not only by host and natural enemy characteristics but also, the application of pesticide to pest population can affected the parameters of functional response as well as efficiency of natural enemy. in this research, the side effects of two pesticides, hexaflumuron and pymetrozin and also acaricide spirodiclofen and plant extracts, caiotropis procera (willd.) r. br. (asclepiadaceae), teucrium polium (labiatae), fumaria parviflora lam. (fumariaceae) and thymus vulgaris l. (labiatae) were studied on functional response of 3rd instars larvae of chrysoperla carnea at 26±1oc, 60±5% rh and 16:8 (l: d). different densities levels (2, 4, 8, 16, 32, 64 and 100) of the 5th instars of common pistachio psylla nymphs agonoscena pistaciae were placed on pistachio leaf disc with 65 mm diameter. treatment of larvae were carried out using dipping method by maximum recommended field rates for pesticide and selected concentration of plant extracts (750 µl/ml). functional response type was determined using logistic regression and the parameters, searching efficiency (a) and handling time (th) were estimated by non-linear regression using sas software. functional response was type iii in f. parviflora treatment and type ii in others. functional response in t. vulgaris was not diagnosed. the lowest and the most searching efficiency were in c. procera treatment (0.0377) and control (0.1209) respectively. handling time was the lowest in c. procera treatment (0.00177 h-1) and the most in hexaflumuron (0.3132 h-1). it could be concluded that pesticide and plant extracts can affect the predation value and functional response of c. carnea to common pistachio psylla. this effect to control, sometimes as a functional response iii and loss of searching efficiency is positive.