So, what's the problem
Rubbervine, Cryptostegia madagascariensis (common name: devil’s claw) is a serious invasive weed. Hailing from Madagascar, it was introduced to Brazil as an ornamental plant but has since invaded the semi-arid northeastern region of the country, especially the unique Caatinga ecosystem. Rubbervine is well adapted to Brazil’s climate, producing a large seed bank and abundant toxic latex, all of which makes its control with conventional methods extremely difficult.
In the Caatinga, the vine is threatening endemic biodiversity such as the three banded armadillo (mascot of the 2014 FIFA world cup) and the Carnauba palm by smothering vast areas of intact forest and forming impenetrable masses that is killing trees and preventing animal and human movement, as well as depleting scarce water resources.
The Carnauba palm (Copernicia prunifera), native to northeast Brazil, is known as the ‘tree of life’ due to its many uses. This palm species is the source of the Carnauba wax, known as the ‘queen of waxes’, which is a valuable natural resource used in polish, skincare and cosmetic products. For over a century, rural populations have been sustainably harvesting carnauba leaves and extracting wax for processing by local industry. Extensive areas with Carnauba plants have already had to be abandoned by harvesters due to invasion by rubbervine. Worth US$120m a year, the many industrial applications of the wax are also under threat, as the palm is the sole source of this natural product.
What is this project doing?
Classical biological control has the potential to offer effective and sustainable management of invasive alien weeds such as devil’s claw. And as successfully undertaken for Australia previously, a team from CABI, with our Brazilian counterparts, is investigating whether a suitable biological control agent could be introduced to Brazil to address the problem of rubbervine invasion.
This biocontrol strategy involves the deliberate release of safe and highly specific natural enemies from the native range of the target weed. The aim is to reduce the abundance of the weed in its introduced range below an ecological or economic threshold. This kind of biocontrol has a proven track record of success and can be a highly cost-efficient approach to control invasive weeds.
The biocontrol agent in mind here is the damaging rust fungus Maravalia cryptostegiae known to infectthe vine in Madagascar. An isolate of the same rust fungus was used to successfully control another rubbervine species in Australia and evidence suggests that this one is equally safe as it is anticipated to be specific, damaging and highly likely to have a similar impact.
The objectives of the proposed project are to undertake ecological baseline studies of the rubbervine invasion in the Cerea State of northeastern Brazil, to match the plant biotype with a virulent rust biotype, to assess the host specificity of the selected pathogen isolate against an agreed test plant list and to evaluate its safety as a potential biocontrol agent for introduction into Brazil.
CABI has internally funded the preparatory phase of this programme and helped to organize an event in Fortaleza, Brazil to raise awareness. This brought together stakeholders and potential sponsors from the governmental, NGO and corporate sectors.
An initial field survey funded by the Brazilian Government has been conducted in the affected region to map the rubbervine infestation. Two isolates of the rust are currently held in storage under liquid nitrogen and a test plant list to evaluate the host specificity of these isolates is being compiled.
With funding, ecological baseline studies of the invasion will be carried out as well as a molecular characterization of the rubbervine biotype in Brazil. This will allow us to pinpoint the Madagascan region of origin more precisely in order to select the best matched pathogen biotype for testing. Since most of the research into the rust has already been carried out during the respective Australian biocontrol project, the focus will be to assess the safety of the rust for the native Brazilian flora. Furthermore, the climatic suitability of selected rust isolates will be assessed with the view to a potential release in the Caatinga. Following any rust release its impact will then be monitored in the field.
Coordinator, Sustainable Crop & Pest Management and Regional Representative - South America
Country Director CABI UK/ Regional Coordinator Invasives Regional Coordinator