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United States Department of Agriculture

Agricultural Research Service

Title: Ecology and management of Sheoak (Casuarina spp.), an invader of coastal Florida, U.S.A.

Authors
item Wheeler, Gregory
item Taylor, G -
item Gaskin, John
item Purcell, M -

Submitted to: Journal of Coastal Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 2009
Publication Date: May 1, 2011
Repository URL: http://hdl.handle.net/10113/50081
Citation: Wheeler, G.S., Taylor, G.S., Gaskin, J.F., Purcell, M. 2011. Ecology and management of Australian pine (Casuarina spp.), an invader of coastal Florida, USA. Journal of Coastal Research. 27(3):485-492.

Interpretive Summary: The results of this analysis illustrate the significance of the Casuarina invasive weed species to coastal habitats in Florida and options for control. One species in particular, C. equisetifolia has become one of the most common coastal species in tropical areas the world over. These species threaten the diversity of coastal vegetation, impact populations of rare or endangered animals, and may increase beach erosion by interfering with the normal processes of sand deposition. Continued cultivation of these species for ornamental purposes or as an agricultural windbreak is particularly shortsighted considering the damage posed to public safety and coastal communities. These species are amenable to biological control in North America as the plant family is taxonomically isolated with no close relatives. Numerous potential biological control candidates have been discovered from surveys conducted in Australia. With few other cost-effective and sustainable options, biological control will be an important component limiting the spread of these invasive species.

Technical Abstract: The Casuarina spp. are invasive weeds in Florida that threaten biological diversity and beach integrity of coastal habitats. The trees include three species and their hybrids that aggressively invade riverine and coastal areas. Of the three species, C. equisetifolia and C. glauca are highly salt tolerant and widespread inhabiting coastal areas. The third species, C. cunninghamiana, invades riverine habitats. These species pose dangers to both the environment and public safety. The environmental damage includes interfering with nesting by endangered sea turtles, American crocodiles and the rare swallow-tailed kite. Additionally, allelochemical leachates reduce germination and establishment of native vegetation. Casuarina-infested beaches are more prone to sand loss and erosion. Moreover, with shallow roots and tall canopies they are among the first trees to fall in high winds and as such restrict evacuation efforts during hurricanes. Control of these species is mostly with herbicides requiring repeated applications and monitoring. One of the most cost-effective means of controlling these invasive species is with classical biological control. Australian surveys for potential biological control agents began in 2004 resulting in the discovery of several promising candidates. These include seed-feeding torymid wasps, defoliating caterpillars and weevils, leaf tip gall-formers from a cecid midge, and sap-feeding psyllids. Continued work is needed to determine the suitability of these species for biological control. Despite conflicts of interest expressed by homeowners who value the trees for shade and windbreaks, there are good prospects for safe and effective biological control of these invasive species.

Last Modified: 10/31/2014