Editing Banksia (section)

===Dieback===
Another threat to ''Banksia'' is the [[water mould]] ''[[Phytophthora cinnamomi]]'', commonly known as "dieback". Dieback attacks the roots of plants, destroying the structure of the root tissues, "rotting" the root, and preventing the plant from absorbing water and nutrients. ''Banksia'''s [[proteoid root]]s, which help it to survive in low-nutrient soils, make it highly susceptible to this [[disease]]. All Western Australian species are vulnerable, although most eastern species are fairly resistant.<ref>{{cite journal |last1=Mccredie |first1=TA |last2=Dixon |first2=KW |last3=Sivasithamparam |first3=K |title=Variability in the Resistance of Banksia L.f. Species to ''Phytophthora cinnamomi'' Rands |journal=Australian Journal of Botany |volume=33 |issue=6 |year=1985 |pages=629–637 |doi=10.1071/BT9850629 }}</ref>

Vulnerable plants typically die within a few years of infection. In [[southwest Australia|southwest]] Western Australia, where dieback infestation is widespread, infested areas of ''Banksia'' forest typically have less than 30% of the cover of uninfested areas. Plant deaths in such large proportions can have a profound influence on the makeup of plant communities. For example, in southwestern Australia ''Banksia'' often occurs as an understorey to forests of [[jarrah]] (''Eucalyptus marginata''), another species highly vulnerable to dieback. Infestation kills both the jarrah overstorey and the original ''Banksia'' understorey, and over time these may be replaced by a more open woodland consisting of an overstorey of the resistant marri (''[[Corymbia calophylla]]''), and an understorey of the somewhat resistant ''[[Banksia sessilis]]'' (parrot bush).<ref name="Impact of Dieback">{{cite web| title=Impacts in WA| work=Managing Dieback| url=http://www.naturebase.net/content/view/213/548/1/2/| publisher=[[Department of Environment and Conservation (Western Australia)]]| access-date=2007-02-21| archive-url=https://web.archive.org/web/20070903013916/http://www.naturebase.net/content/view/213/548/1/2/| archive-date=3 September 2007| url-status=dead}}</ref>

A number of species of ''Banksia'' are threatened by dieback. Nearly every known wild population of ''B.&nbsp;brownii'' shows some signs of dieback infection, which could possibly wipe it out within years.<ref name="SPRAT brownii">{{SPRAT | id=8277 | name = Banksia brownii}}</ref><ref name="Brown 1998">{{cite book |editor1-last=Brown |editor1-first=Andrew |editor2-last=Thomson-Dans |editor2-first=Carolyn |editor3-last=Marchant |editor3-first=Neville | year = 1998 | title = Western Australia's Threatened Flora | location = Como, Western Australia | publisher = Department of Conservation and Land Management | isbn = 978-0-7309-6875-7 | oclc = 183084186}}{{Page needed|date=August 2016}}</ref> Other vulnerable species include ''B.&nbsp;cuneata'', and ''B.&nbsp;verticillata''.

Dieback is notoriously difficult to treat, although there has been some success with [[phosphite]] and [[phosphorous acid]], which are currently used to inoculate wild ''B.&nbsp;brownii'' populations. However this is not without potential problems as it alters the soil composition by adding [[phosphorus]]. Some evidence suggests that phosphorous acid may inhibit proteoid root formation.<ref name="Murdoch">{{cite web | work = Second International IUFRO meeting | title = Phytophthora in forests and natural ecosystems | url = http://wwwscience.murdoch.edu.au/conf/phytophthora/abstract-wed.html | publisher = [[Murdoch University]] | access-date = 2006-06-26 | archive-url = https://web.archive.org/web/20060720090304/http://wwwscience.murdoch.edu.au/conf/phytophthora/abstract-wed.html | archive-date = 20 July 2006 | url-status = dead }}</ref>

Because dieback thrives in moist soil conditions, it can be a severe problem for banksias that are watered, such as in the cut flower industry and urban gardens.