Daily consumption and functional response of Stethorus gilvifrons (Coleoptera: Coccinellidae) and Orius albidipennis (Hemiptera: Anthocoridae) to Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most economically important pests on a wide range of crops around the world. Consumption rate and functional responses of all larval stages, male and female of Stethorus gilvifrons (Mulsant) and Orius albidipennis (Rueter) to the varying densities of eggs, protonymphs and females of T. urticae were evaluated under laboratory conditions (27 ± 1 °C, 65 ± 5% RH and 16L/8D h photoperiod). Functional response type was determined by a logistic regression model. The Rogers model was used to estimate attack rate (a) and handling time (Th). The results indicated that the functional responses of different stages of two predators were type III on T. urticae eggs and type II on T. urticae protonymphs and females. The shortest handling time (Th) of both predators were observed on eggs followed by protonymphs and females of T. urticae. The highest and the lowest attack rate (a) were observed by the male and first instar larva in S. gilvifrons and female and first instar nymph in O. albidipennis respectively. The maximum daily attack rates (T/Th) were 153.5, 114.4 and 76.07 for S. gilvifrons, and 134.1, 91 and 55.3 for O. albidipennis by feeding on egg, protonymph and female T. urticae respectively. The handling time (Th) of S. gilvifrons adults were shorter than that of O. albidipennis. The results suggested that both predators exhibited suitable efficacy on all stages of T. urticae, however S. gilvifrons acted more effectively than the other predator in laboratory conditions considering higher consumption rate, shorter handling time and higher attack rate.