Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/28/2007
Publication Date: 9/8/2008
Citation: Tipping, P.W., Martin, M.R., Pratt, P.D., Center, T.D., Rayamajhi, M.B. Suppression of growth and reproduction of an exotic invasive tree by two introduced insects. Biological Control. 44(2):235-241.2008. Interpretive Summary: The introduction of two insect biological control agents has resulted in substantial declines in the growth and reproduction of Melaleuca quinquenervia, an invasive exotic tree from Australia. Repeated defoliation by a weevil, Oxyops vitiosa, resulted in stunted growth and minimal seed production over a two year period. Feeding by a psyllid, Boreioglycaspis melaleucae, may have reduced leaf biomass by causing premature leaf drop. Both species are well established throughout the range of M. quinquenervia in Florida and may be limiting the capacity of this tree to spread any further.
Technical Abstract: The invasive tree Melaleuca quinquenervia experienced substantial declines in growth and reproduction in response primarily to chronic herbivory by the defoliating weevil Oxyops vitiosa. Herbivory was mediated on individual trees using regular applications of the insecticide acephate during a 2-year period to minimize populations of O. vitiosa and later the phloem-feeding psyllid, Boreioglycaspis melaleucae. Half of the trees also received drip irrigation to evaluate the influence of water on plant responses to herbivory. Insecticide-protected trees grew in height nearly six times faster and became 108% taller. In contrast, unprotected trees produced only 19% as much woody biomass, 13% as much leaf biomass, and 0.9% as much seed as protected trees. The mean (+ SE) of total above ground biomass was 873.07 + 191.37 g in unsprayed trees and 3856.28 + 491.58 g in sprayed trees. Unprotected trees produced more stem tips per unit of height, which produced a more bushy habit. Greater amounts of water did increase leaf biomass, but all other plant variables were influenced most by herbivory. The seed-fueled invasive capacity of melaleuca will likely be checked in areas favorable to the population dynamics of the biological control agents, especially O. vitiosa.