[Scientific Papers] http://www.scipapers.com    2007-11-16  

Trophic interactions between two herbivorous insects, Galerucella calmariensis and Myzus lythri, feeding on purple loosestrife, Lythrum salicaria, and two insect predators, Harmonia axyridis and Chrysoperla carnea

Bethzayda Matos and John J. Obrycki¹

Department of Entomology, Iowa State University, Ames IA 50011
¹ Department of Entomology, University of Kentucky, Lexington KY 40546


Abstract

The effects of two herbivorous insects, Galerucella calmariensis Duftschmid and Myzus lythri L. (Coleoptera: Chrysomelidae), feeding on purple loosestrife, Lythrum salicaria L. (Myrtiflorae: Lythraceae), were measured in the presence of two insect predators, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae). A greenhouse cage experiment examined the direct effects of these predators on these herbivores, and indirect effects of predation on aboveground biomass, defoliation, number of leaves, and internode length. Eight treatment combinations with G. calmariensis, M. lythri, H. axyridis and C. carnea were applied to caged L. salicaria. The experiment ended when G. calmariensis adults were observed, 11 to 13 days after release of first instar G. calmariensis. G. calmariensis larvae alone removed significant amounts of leaf tissue and reduced the number of L. salicaria leaves. Predators did not reduce levels of defoliation by G. calmariensis. C. carnea had no effect on G. calmariensis survival, but H. axyridis reduced G. calmariensis survival in the presence of M. lythri. Both predators reduced the survival of M. lythri. This short duration greenhouse study did not demonstrate that predator-prey interactions altered herbivore effects on L. salicaria.

Keywords: trophic cascade, biological control of weeds, predator-prey interactions


Correspondence: bmatos@iastate.edu, John.Obrycki@uky.edu

Received: 16 May 2006 | Accepted: 26 October 2006 | Published: 10 May 2007


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