|VAN, THAI - Retired ARS Employee|
|Dray, F Allen|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2007
Publication Date: 6/1/2007
Citation: Center, T.D., Pratt, P.D., Tipping, P.W., Rayamajhi, M.B., Van, T.K., Dray Jr., F.A., Wright, S.A. Initial impacts and field validation of host range for Boreioglycaspis melaleucae Moore (Hemiptera: Psyllidae),a biological control agent of the invasive tree Melaleuca quinquenervia (Cav.) Blake (Myrtales: Myrtaceae: Leptospermoideae. Environmental Entomology. 36(3):569-576. 2007.
Interpretive Summary: Diversion of water flow from the Everglades during the 1950s allowed exotic species to invade previously undisturbed, pristine habitats. Foremost amongst these invaders was the Australian melaleuca tree which usurped a half million acres. A massive effort is underway to restore the natural water flow, but this will not eliminate melaleuca, which has indelibly modified many critical habitats making them more vulnerable to wildfires. Melaleuca has also increased soil elevations creating drier conditions. Removal of these pernicious trees is therefore a necessary part of Everglades restoration. Biological control is being implemented to assist in this effort by hampering the trees ability to re-establish in areas where it has been removed. Plant-feeding insects imported from Australia are being released after long-term testing ensures that they will not harm other plants. Most recently, a psyllid or plant louse was released to compliment the earlier release of a weevil. The psyllid has begun to impact melaleuca by reducing regrowth from cut stumps and killing seedlings. It will take a while before we can determine its effect on larger trees, but initial results look promising. A common garden study also confirmed laboratory results that indicated that this insect will not attack anything other than melaleuca.
Technical Abstract: Invasion of south Florida wetlands by the Australian paperbark tree (“melaleuca”), Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca) has caused adverse economic and environmental impacts. The tree’s biological attributes along with favorable ambient biophysical conditions combine to complicate efforts to restore and maintain south Florida ecosystems. Management requires an integrated strategy that deploys multiple biological control agents to forestall reinvasion and to supplement other control methods thereby lessening recruitment and regeneration after removal of existing trees. This biological control program began during 1997 when an Australian weevil (Oxyops vitiosa) was released. A second Australian insect, the melaleuca psyllid (Boreioglycaspis melaleucae) first introduced during 2002, has also widely established. After inoculation of the psyllid in a field study, only 40% of seedlings survived herbivory treatments compared to 95% survival in controls. The resultant defoliation also reduced growth of the surviving seedlings. A weevil-induced decline at a site comprised mainly of coppicing stumps had slowed after a 70% reduction. Psyllids then colonized the site and 37% of the remaining coppices succumbed. The realized ecological host range of B. melaleucae was restricted to M. quinquenervia while 18 other non-target plant species predicted to be suboptimal or non-hosts during laboratory host range testing were unaffected when interspersed with psyllid-infested melaleuca trees in a common garden study. Evaluations are ongoing, but B. melaleucae is clearly reducing seedling recruitment and stump regrowth without adversely impacting other plant species. Manifestation of impacts on mature trees will require more time but initial indications suggest that the psyllid will be an effective biological control agent.