DEVELOPMENT & EVALUATION OF BIOLOGICAL CONTROL AGENTS FOR INVASIVE SPECIES THREATENING THE EVERGLADES & OTHER NATURAL AND MANANGED SYSTEMS
Location: Invasive Plant Research Laboratory
Title: Hard Evidence for Melaleuca Biocontrol
Submitted to: Biocontrol News and Information
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 29, 2009
Publication Date: March 1, 2009
Citation: Tipping, P.W., Martin, M.R., Nimmo, K., Pierce, R., Smart, M., White, E., Madeira, P.T., Center, T.D. 2009. Hard Evidence for Melaleuca Biocontrol. Biocontrol News and Information 30:3N.
Interpretive Summary: Classical biological control using insects is reducing the negative effects of Melaleuca quinquenervia, a serious ecological weed of the Florida everglades. Damaging populations of this exotic, invasive tree were reduced by almost half when subjected to continual attack from two biocontrol agents. In addition, trees in attacked populations produced no seeds, died in greater numbers, and actually lost height as compared to melaleuca populations that were protected from the biocontrol agents with regular applications of insecticides. This long term experiment provides irrefutable evidence of the population level suppression of this weed using classical biological control instead of herbicides or mechanical methods.
The population dynamics of a cohort of Melaleuca quinquenervia were monitored over a 5-y period in a cypress-pine wetland while subjected to two levels of herbivory. The trees were recruited during 1998-1999 after a destructive crown fire. Half of 26 experimental plots were sprayed every 4-6 weeks with a broad spectrum insecticide to reduce herbivory by the biological control agents Oxyops vitiosa and Boreioglycaspis melaleucae. After only 1 y melaleuca density increased 26% in sprayed plots and 7% in unsprayed plots. However, over the entire 5-y period melaleuca density increased in sprayed plots by 0.1% while decreasing 47.9% in unsprayed plots when compared to initial densities. Annual mortality of melaleuca never exceeded 6% in any year in sprayed plots while ranging from 11 to 25% in unsprayed plots. Limited seed production occurred on sprayed trees but never on unsprayed trees. Mean tree height increased 19.6% in sprayed plots while declining 30.6% in unsprayed plots. Coverage by native vegetation increased with decreasing melaleuca density. This is the first study with controls that quantifies the population level regulation of melaleuca by introduced biological control agents and corroborates other correlative studies that documented significant changes in melaleuca communities after the introduction and establishment of biological control agents.