Effect of temperature on biological characteristics and feeding capacity of Episyrphus balteatus (Diptera: Syrphidae) as important predator of the currant lettuce aphid, Nasonovia ribisnigri (Hemiptera: Aphididae)

Biological characteristics and feeding rate of Episyrphus balteatus on Nasonovia ribisnigri as an economically important pest of lettuce were evaluated at four constant temperatures (15, 20, 25 and 30 ± 1°C), 65 ± 5% RH and a photoperiod of 16L: 8D h. Results showed that the developmental time of the incubation period (egg), first and third instars larvae and pupae of E. balteatus significantly decreased with increasing temperature. Moreover, the duration of developmental time (total immature stages) of this predator decreased with increasing temperature from 24.43 days at 15°C to 13.94 days at 30°C. The feeding rate of E. balteatus was effected by larval instars and temperatures. The 24-hour feeding rate of total larval instars of the predator were 11.48, 13.9, 11.97 and 9.32 nymphs / larva at examined temperatures, respectively.There were no significant differences regarding the developmental time and 24-hour feeding rate of the second larval instar at studied temperatures. The least mortality rate and the greatest 24-hour feeding rate were 12% and 11.6±0.62 third instar nymphs of N. ribisnigri / larva, respectively, in third instar larvae of E. balteatus at 20°C. According to the obtained results and considering high feeding rate of E. balteatus especially at 20°C, seems this predator can be considered as one of the suitable elements for the integrated pest management program of currant lettuce aphid.