واکنش تابعی کفشدوزک Hippodamia variegata نسبت به تراکم‌های مختلف شته‌یSchizaphis graminum روی دو رقم گندم

The lady beetle Hippodamia variegata (Goeze) is one of the important predators of aphids in Iran. In this study, the functional response of male and female adult of this predator was investigated to the four-day-old nymphs of Schizaphis graminum (Rondani) on two wheat cultivars, Ehsan and Tirgan. The experiments were carried out at 25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16: 8 (L: D) h in 10 replicates. Five seeds of each wheat cultivar were sown separately in transparent plastic containers (12 cm in height and 9 cm in diameter) and the seedlings were used in the experiments when their height reached 12 cm. The aphid nymphs in densities of 2, 4, 8, 16, 32, 64, 96, 128 and 160 were separately offered to adult male and female predators in containers containing wheat seedlings. After 24 h, the predators were removed from experimental arenas and the number of preys consumed was recorded. The type of functional response was determined by logistic regression analysis and the parameters of attack rate and handling time were estimated using PROC NLIN procedure of SAS. Adult male and female predators exhibited functional response type II on both wheat cultivars. On Ehsan cultivar, attack rate and handling time for female predator were estimated to be 0.3144±0.1707 h-1 and 0.1485±0.0139 h and for male predator were 0.0711±0.00804 h-1 and 0.1379±0.0131 h, respectively. These parameters on Tirgan cultivar were 0.1246±0.0176 h-1 and 0.1653±0.00953 h for female, and 0.0493±0.00399 h-1 and 0.1516±0.0135 h for male, respectively. This research revealed that predation rate of both male and female adult of H. variegata to S. graminum is inversely density dependent on both wheat cultivars. However, supplementary studies under field conditions are needed to provide further details of predator-prey interactions.