Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2005
Publication Date: 4/5/2006
Citation: Franks, S., Kral, A., Pratt, P.D. 2006. Herbivory by introduced insects reduces growth and survival of melaleuca. Environmental Entomology. 35(2):366-372. Interpretive Summary: Melaleuca quinquenervia (melaleuca) is a native to eastern Australia and has been introduced to various locations around the world. One hundred years after its introduction into Florida, melaleuca grows spontaneously and displaces native plants as well as animals in the wetlands that comprise the Florida Everglades. In an effort to curb the invasion of this weed, scientists have identified natural enemies or biological control agents that help in the suppression of melaleuca. This article provides details on the introduced biological control agent Boreioglycaspis melaleucae, with emphasis on the effects feeding has on seedling survivorship and growth.
Technical Abstract: We investigated the influence of herbivory by two introduced insect herbivores on the survival and performance of Melaleuca quinquenervia (Cav.) Blake (Myrtaceae) seedlings, an invasive tree that threatens the Florida Everglades ecosystem. Boreioglycaspis melaleucae (Moore) (Homoptera: Psyllidae) nymphs and Oxyops vitiosa (Pascoe) (Coleoptera: Curculionidae) larvae were transferred onto Melaleuca seedlings within replicated 1/4 m2 caged plots in Palm Beach County, Florida. The treatments included three densities of first and second Boreioglycaspis instars at one, 15, and 50 nymphs per seedling, one treatment of a single first or second Oxyops larval instar per seedling, another treatment of both one Oxyops larva and one Boreioglycaspis nymph per seedling, and caged and uncaged controls. Herbivory by Oxyops did not affect Melaleuca seedling height, leaf number, or survival. Feeding by Boreioglycaspis decreased survival, height, and leaf number, with these measures of plant performance approximately 50% lower in the high and medium densities compared with the low/zero density treatments. In a field plot adjacent to the experimental area, we measured growth, survival, and naturally occurring insect density and damage on 1,100 seedlings. Although insect densities were on average lower in the field plot than in the experiment, mortality and growth rates of the seedlings were comparable to those in the experiment. The results indicate that above a threshold density, Boreioglycaspis herbivory may be effective in reducing growth and survival of Melaleuca at the potentially critical seedling life stage. It also appeared that effects of the insects were independent rather than antagonistic or synergistic.