Cryptostegia grandiflora (Rubber Vine): An Invasive Weed.

Cryptostegia grandiflora or as it is commonly know the rubber vine, is a woody-perennial vine that is native to the southern regions of Madagascar. The rubber vine has become a significant weed in northern Australia, with some environmentalists regarding it as the one of, if not the worst weed in Australia at present. It has been introduced into many other tropical and subtropical regions as a ornamental plant because of its attractive flowers and because of the commercial quality natural latex rubber found in the sap of the vine (McFadyen & Marohasy, 1990).

Since its introduction into Northern Australia in 1917, rubber vine has spread to an excess of 30,00km²  of tropical Queensland. From the initial infestations alongside rivers, dense impenetrable thickets have become established, these tickets can cover trees up to 30m tall and can choke out all the native vegetation, it then progressively invades the surrounding areas (McFadyen & Harvey, 1990).

            Rubber vine in bloom (www.devereuxgardens.com).  Assessed on the 23rd of March 2014.                                           

Another one of the reasons why rubber vine is so devastating to Australia's native environment is its extreme toxicity. Less than 10g of rubber vine leaves can kill a 400kg horse within 6 days. It is highly toxic to sheep, cattle and goats. It has an unpalatable taste but during the dry season when grass is scarce many animals turn to the rubber vine as a last resort and as a consequence many perish. This can have a major effect on the lively hoods of cattle farmers with rubber vines on their properties (Land Protection, QDNRME 2004).

    Infestation of rubber vine in north Queensland (daff.qld.gov.au).Assessed on the 23rd of March 2014.

The highly specific rust fungus Maravalia crypto-stegiae was released during the summers of 1993-1994 by Lands Department and in 1994-1995 by the Queensland Department of Natural Resources. Long-term monitoring sites established in 1997 to evaluate the efficacy of the rust. At al the sites, there has been at least a 40% reduction in the number of live plants and stems per hectare, more than a 10% reduction in the number of live stems per plant and a significant reduction in seedling recruitment from 178 hectares to almost 0 in 2001(Lindsay & Vogler, 2002).

References:

•  R. E. McFadyen, J. J. Marohasy, 1990. A leaf feeding moth,Euclasta whalleyi (Lep.: Pyralidae) for the biological control of Cryptostegia grandiflora (Asclepiadaceae) in Queensland, Australia. Entomophaga 1990, Volume 35, Issue 3, pp 431-435
• R. E. McFadyen, G. E. Harvey, 1990. Distribution and Control of Rubber Vine, Crypotostegia grandiflora, a major weed in northern Queensland. Plant Protection Quarterly, 1990 Vol. 5 No. 4 pp. 152 - 155.
• Land Protection, Queensland Department of Natural Resources, Mines and Energy. Rubber Vine Management  March 2004.
• A. Lindsay, W. Vogler, 2002. "The impact of the rust fungus Maravalia cryptostegiae on three rubber vine (Cryptostegia grandiflora) populations in tropical Queensland." 13th Australian weeds conference ‘‘Threats now and forever. 2002.