Predation by Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) on immature Rhagoletis mendax Curran (Diptera: Tephritidae) in semi-field and field conditions

J. M. Renkema^1*, D. H. Lynch², G. C. Cutler³, K. MacKenzie⁴ and S. J. Walde¹

Abstract
Practices that enhance abundance and diversity of generalist predators are often employed with the objective of improving biological control of insect pests. Ground beetles and other predators can prey on blueberry maggot, an important pest of blueberries, when mature larvae pupate in the ground.

We conducted mesocosm and field experiments to determine if Pterostichus melanarius, a common predatory ground beetle, lowers maggot numbers in compost mulch or when predator and alternative prey abundances are manipulated.

At background (field) densities of alternative prey, increasing densities of P. melanarius did not significantly reduce pest numbers in mesocosms containing compost or soil. When alternative prey were removed from compost, beetles reduced pest numbers by up to 35%. In field experiments, maggot numbers were higher when beetles and other predators were excluded from soil plots, but beetle exclusion had no effect in compost plots where both predator and alternative prey numbers were high.

Our results indicate that there can be some reduction of blueberry maggot by P. melanarius and other potential predators when there are few alternative prey. However, despite attracting large numbers of predators compost mulch did not lead to a significant reduction in blueberry maggot; in fact, the high abundance of alternative food associated with compost appeared to interfere with beetle predation on blueberry maggot.


Source
Biological Control (2012) 60: 46-53
DOI: .1016/j.biocontrol.2011.10.004


Author Locations and Affiliations
(1) Department of Biology, Dalhousie University, 1355 Oxford St., Halifax, Nova Scotia, Canada B3H 4J1
(2) Department of Plant and Animal Science, Nova Scotia Agricultural College, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3
(3) Department of Environmental Sciences, Nova Scotia Agricultural College, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3
(4) Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, 4200 Highway #97, South, Summerland, British Columbia, Canada V0H 1Z0
* Corresponding author, E-mail jrenkema@nsac.ca


Posted January 2012