Stumpout: The Weed Killing Mycoherbicide
Stumpout®: Protecting Indigenous Fauna with a Fungus
Black and golden wattle trees (Acacia mearnsii and Acacia pycnatha) are considered an invasive alien species in South Africa, they out-compete and replace local fauna and consume more water than many of their indigenous counterparts. Cylindrobasidium laeve, is a fungus that is indigenous to South Africa. ARC has harvested it from dead black wattle stumps, where it was found to have a unique property as a biological control agent to prevent coppice growth of felled Wattles. Cylindrobasidium laeve is saprophytic, meaning the fungus feeds on dead organic matter, such as rotting wood. We have since developed this fungus into Stumpout®, a user-friendly and affordable treatment to prevent cut stumps of black and golden wattles from resprouting after felling. By applying Stumpout® to the felled or burned stump of the wattle, it prevents regrowth and further prevents multi-stemmed trees from developing. Multi-stemmed trees are more difficult and more expensive to control and thus more difficult to clear. Stumpout® is predominantly used during the summer months, although it can be applied all year round. ARC is focusing on producing fresh batches in spring and early summer. The great advantage of Stumpout® is it is harvested near George and Joubertina in the Western and Eastern Cape, creating local job opportunities. Further, it is completely environmentally friendly, user-friendly and very affordable. It is not a pathogen or a chemical herbicide and thus has none of the negative environmental impacts of those approaches to eradicate Wattle species. Stumpout® is, therefore, safe to use in areas close to water sources without concern for contamination.
Black wattles (Acacia mearnsii) and golden wattles (Acacia pycnatha) are a serious invaders in South Africa, and every year large amounts of money and time are spent by the Department of Environmental Affairs: National Resource Management Programme (DEA: NRMP in the Working for Water Campaign) as well as by private land owners clearing their invaded land. Felled trees must be treated with herbicides or other poisons to prevent them from simply coppicing, which results in invader trees regrowing as multi-stemmed trees, which are even more difficult and costly to remove as they form a more dense stand of trees. However, herbicides can have negative environmental impacts, especially in sensitive ecosystems such as riparian zones. A non-toxic alternative to herbicides would avoid these impacts.
ARC has developed Stumpout® derived from an indigenous fungus, Cylindrobasidium laeve, which occurs naturally on rotting or dying tree stumps. Due to its saprophytic activity, Stumpout® presents a safe way of preventing the regrowth of the stumps of felled black and golden wattles. It contains the fungal spores of Cylindrobasidium laeve. The spores are drawn into the wattle stump as it dries after felling, the spores then germinate once inside the stump and the fungus will start to grow. Thus when Stumpout® is applied to the cut stump, the non-toxic fungus grows downwards and eventually colonises the entire stump, all the while decomposing the stump and eventually killing the plant. Mortality of treated stumps is between 80% and 100%. Stumps cut no higher than ankle height usually die within 3 months, stumps cut approximately 30 cm high may, however, take up to a year to die. ARC is not aware of any other non-poisonous product for the control of alien and invasive tree species, and thus we consider this product a world first.
While he has since left the ARC, Dr Mike Morris, the former manager of the Weed Pathology Unit, isolated and developed the product Stumpout®. Current production of the Stumpout® product and order receipts is carried out by Ms Gwen Samuels. Finally Dr Alan Wood, who is the current manager of the Weed Pathology Unit, has taken lead on the project.