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United States Department of Agriculture

Agricultural Research Service

Title: Natural enemy density and soil type influence growth and survival of Melaleuca quinquenervia seedlings

Authors
item Sevillano, Lucero -
item Horvitz, Carol -
item Pratt, Paul

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 26, 2010
Publication Date: January 26, 2010
Citation: Sevillano, L., Horvitz, C., Pratt, P.D. 2010. Natural enemy density and soil type influence growth and survival of Melaleuca quinquenervia seedlings. Biological Control, Volume 53, Issue 2, May 2010, Pages 168-177

Interpretive Summary: Multiple insects are commonly introduced as biological control agents to reduce growth and spread of invasive plants. Little is known about the species-specific contributions of co-existing agents, and about insect density needed to control of invasive plants. We investigated the effects of insect type and density on seedling survival and growth of the invasive tree Melaleuca quinquenervia, in Florida. The biological control agents are the weevil, Oxyops vitiosa, and the psyllid, Boreioglycaspis melaleucae. We conducted a three-way factorial shade-house experiment, manipulating weevil density (three levels), psyllid density (three levels), and soil type (organic/sandy). We found that weevil and psyllid densities significantly affected plant performance. Survival was only reduced by high insect densities, and psyllids had stronger effects than weevils. Overall, seedlings increased in size most rapidly in the controls (no insects) and least rapidly at high insect densities. Psyllids also had a stronger effect than weevils on growth (height and diameter). For some of the growth parameters, the effects of one type of insect depended both on the density of that insect and on the density of the other insect. Soil type also influenced plant growth and for some growth parameters, the response of plants to herbivory. The standing crop of leaves at the end of the experiment was highest at intermediate rather than at zero or high insect densities, which reveals the ability of M. quinquenervia seedlings to compensate for herbivory. Our results show that insect type and density influence the effectiveness of biological control on M. quinquenervia seedlings.

Technical Abstract: Multiple insects are commonly introduced as biological control agents to reduce growth and spread of invasive plants. Little is known about the species-specific contributions of co-existing agents, and about insect density needed to control invasive plants. We investigated the effects of insect type and density on seedling survival and growth of the invasive tree Melaleuca quinquenervia, in Florida. The biological control agents are the weevil, Oxyops vitiosa, and the psyllid, Boreioglycaspis melaleucae. We conducted a three-way factorial shade-house experiment, manipulating weevil density (three levels), psyllid density (three levels), and soil type (organic/sandy). We found that weevil and psyllid densities significantly affected plant performance. Survival was only reduced by high insect densities, and psyllids had stronger effects than weevils. Overall, seedlings increased in size most rapidly in the controls (no insects) and least rapidly at high insect densities. Psyllids also had a stronger effect than weevils on growth (height and diameter). For some of the growth parameters, the effects of one type of insect depended both on the density of that insect and on the density of the other insect. Soil type also influenced plant growth and for some growth parameters, the response of plants to herbivory. The standing crop of leaves at the end of the experiment was highest at intermediate rather than at zero or high insect densities, which reveals the ability of M. quinquenervia seedlings to compensate for herbivory. Our results show that insect type and density influence the effectiveness of biological control on M. quinquenervia seedlings.

Last Modified: 11/23/2014
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