Functional Response of Fourth Instar Larvae and the Female Serangium montazerii Fursch (Coleoptera: Coccinellidae) to Different Densities of Dialeurodes citri (Ashmead) (Hemiptera: Aleyrodidae) Under Laboratory Conditions

Abstract

Functional responses of fourth instar larvae (L4) and the female, Serangium montazerii Fursch to different densities (5, 10, 20, 30, 40, 60, 80 and 100 for females and a more 120 whiteflies for L4) of third and fourth instar nymphs of Dialeurodes citri were studied. These experiments were carried out in a growth chamber (25ËšC, 65 ± 5% RH and a photoperiod of 16L: 8D h) on Thompson navel, Citrus sinensis cv. Thompson leaves. Each experiment was replicated five times. Using logistic regression, a type II functional response was determined for two stages of S. montazerii. The searching efficiency (a’) and handling times (Th) of the female adults and larvae by using Nonlinear least-square regression were estimated as 0.1614±0.0456 h-1, 0.2540 ± 0.0587h-1 and 0.4641 ± 0.0377h-1, 0.3715 ± 0.0174 h-1, respectively. Maximum theoretical predations (T/Th) estimated by the model of Rogers for larvae and females were 64.60 and 51.71, respectively. Although fourth instar larvae are more efficient than female, both life stages of S. montazerii may have the potential to be employed in biological control programmes against citrus white fly.