Effect of host plant on the functional response of the predator Podisus nigrispinus (Heteroptera: Pentatomidae)

Effect of host plant on the functional response of Podisus nigrispinus females to densities of fourth instar Spodoptera exigua was investigated using potted sweet pepper, eggplant, and tomato plants. Logistic regression analysis revealed a type II response on sweet pepper and eggplant, but a type III response on tomato. The results were analyzed by both the random predator and disc equations. Attack rates (a) on sweet pepper and eggplant were estimated by the disc equation to be 0.048 h(-1) and by the random predator equation to be 0.093 and 0.108 h(-1), respectively. On tomato, attack rate was a function of prey density (a = bN), with b averaging 0.006 and 0.008 for the disc and random predator equations, respectively. Handling times (Th) On eggplant and sweet pepper were similar, with estimated values of 2.5-2.8 h for the disc equation and 3.0-3.2 h for the random predator equation. Predators showed significantly greater handling times on tomato, with an estimated value of 5.6 h in both models. In an additional experiment, residence of nymphal predators on the different plants was compared in the absence of prey. Predators were found in over 60% of cases on eggplant and sweet pepper plants but only in 25% of cases on tomato plants. It is suggested that glandular trichomes on the plant surface and allelo-chemicals may interfere with the predator's performance on tomato, resulting in an impaired searching efficiency and predation ability. (C) 2000 Academic Press.