Response of Encarsia citrina and Encarsia perniciosi (Hymenoptera: Aphelinidae) to Diaspidiotus perniciosus (Hemiptera: Diaspididae) with particular emphasis on temperature-dependent functional response of E. perniciosi

Prior to the field release of natural enemies in biocontrol programs, it is essential to evaluate their efficiency under laboratory conditions. One of the most informative methods is studying the functional response of natural enemy. Moreover, temperature is an important factor that affects the efficiency of biocontrol agent. Firstly, this study examined the effect of host density of the diaspidid insect, Diaspidiotus perniciosus (Comstock) on functional response of the aphelinid parasitoids, Encarsia perniciosi (Tower) and Encarsia citrina Craw (cf. Ben-Dov. et al., 2012 in ScaleNet). Secondly, based on the obtained results from the first experiment, we evaluated the temperature-dependent functional response only for E. perniciosi. Three constant temperatures (15, 20, and 25 °C) and five host densities (10, 15, 20, 25, and 30 2nd instar) were used. At each densitytemperature combination, a female E. perniciosi (48 h old) was released for a 24 h. In the first experiment, the decelerating rate of decrease in the parasitism rate of E. perniciosi indicated a type II response, whereas the absence of significant dependence on host density by E. citrina indicated a type I response. In the second experiment, the daily rate of oviposition per female of E. perniciosi was significantly increased when temperature and host density increased, however, the type of response (i.e. type II) did not alter with increasing temperature. The attack rate for E. perniciosi increased with increasing temperatures from 15 to 25 °C, whereas the handling time decreased. The 25 °C seems to be the most suitable condition for Encarsia activity and reproduction. This implies that E. perniciosi is well adapted to relatively moderate temperature, which allows its implementation as a biocontrol agent against D. perniciosus during the growing season even in countries of higher latitudes