Predation, functional response and demographic parameters of Orius albidipennis (Hemiptera:Anthocoridae) on Schizaphis graminum (Hemiptera:Aphididae): effect of host plant morphological attributes

Plant attributes like leaf hairiness and trichome compactness diversely affect the biocontrol agents of phytophagous insect pests. In the current study, effect of physical plant features on life table characteristics and functional response of Orius albidipennis (Rueter) females feeding on Schizaphis graminum (Rondani) was investigated on two common wheat cultivars (Falat and Pishtaz) differing in leaf morphological features. The trichome density of wheat cultivars considerably influenced a broad spectrum of attributes related to the performance of O. albidipennis. The intrinsic rate of increase (rm) was significantly greater on Falat (0.09±0.006) than on Pishtaz (0.06±0.008) cultivar. Similarly, the net reproductive rate and finite rate of increase were greater on Falat (16.72±3.38 and 1.083±7.54) than on Pishtaz (8.08±2.04 and 1.067±9.49). Although Orius predators exhibited type III of functional response on both wheat cultivars, they had lesser searching efficiencies and higher handling times on Pishtaz than those on Falat cultivar. Moreover, the maximum attack rate (T/Th) was greater on Falat than on Pishtaz. Lesser maximum predation and greater handling time of the Orius predators on Pishtaz cultivar might be imputed to the significantly more condensed surface trichomes of its leaves than that of Falat leaves, which physically prevented movement of the Orius bugs and decreased prey encounter rate. Moreover, increase of trichome density negatively influenced on foraging behavior of the predatory bug. Females were also found to prefer wheat leaves with fewer trichomes as oviposition hosts. It seems that trichomes provided hinderance to the orius bug. To recapitulate, it could be stated that the efficiency of O. albidipennis in controlling S. graminum on wheat may be more beneficial in cultivars with lower trichome density.