Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2012
Publication Date: 1/31/2013
Citation: Xiao, Y., Osborne, L., Chen, J., McKenzie, C.L. 2013. Functional responses and prey-stage preferences of a predatory gall midge and two predacious mites with twospotted spider mites, Tetranychus urticae as host. Journal of Insect Science. 13:8. Available: http://www.insectscience.org/13.8. Interpretive Summary: Current developments in integrated pest management in greenhouses have shown the need to increase the number of potential natural enemies to manage different pests that attack greenhouse crops. Functional response evaluates the effectiveness of predacious insects and mites to their prey by using mathematical models to categorize their efficiency as biological control agents. This study was conducted to evaluate and compare the potential role of three commercially available predators, predatory gall midge and two new predacious mite species as biological control agents of twospotted spider mite. These experiments combined with our other experiments confirmed the potential of the three predator species evaluated as solid biological control agents for the management of T. urticae in greenhouse vegetable production.
Technical Abstract: The twospotted spider mite, Tetranychus urticae (Acari: Tetranychidae), is an important pest of vegetables and other crops. This study was conducted to evaluate and compare the potential role of three commercially available predators, predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae), new predacious mite species, Amblyseius swirskii, and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), as biological control agents of T. urticae. The functional responses at prey densities and prey-stage preferences (when offered T. urticae eggs and nymphs) of these predators were investigated under laboratory conditions. F. acarisuga was highly effective and the two species of predacious mites were modestly effective in regulating T. urticae egg densities. Logistic regression analysis suggested a Type II (convex) functional response for all three species: the numbers of prey consumed increased with prey density up to a maximum point after which it slowly began to decrease. The maximum daily predation was recorded (50 eggs / female / day) by larva F. acarisuga at a prey density of over 100 T. urticae eggs per arena, followed by female N. californicus (26 eggs /day) and female A. swirskii ( 15 eggs /day) at a density of 70-79 eggs per arena. Our results on prey-stage preferences showed that all three predator species exhibited no-prey stage preference to prey eggs or nymphs. Among the three species, F. acarisuga had the highest predation potential, in particular at high prey densities. These results are discussed in relation to feeding behavior and the habits of the phytoseiids and their potential for biological control of T. urticae in greenhouse vegetable production.