Grassroots September 2016, Vol. 16, No. 3 | Page 39

Congress Workshop: Invasive Species Elbé Hugo T ARC (Grain Crops Institute), Potchefstroom [email protected] he 51st Annual Congress of the Grassland Society of Southern Africa was recently held at The Wilderness Hotel in Wilderness and was followed by an Invasive Species Workshop which was held on the last day of the congress. The Workshop was organised partly by the Society’s organising committee and partly by Dr PJ Pieterse. Fifty one delegates from across environmental, pasture, forest and agricultural fields involved in invasive species attended the Workshop. There were nine guest speakers covering veld management with regard to invasive plants in rangeland and its control strategies. Dr Sue Milton, a veteran in her field, gave an informative overview with regard to the differences between invaders and survivors. Typical invader species lack natural enemies, produce abundant seed that can be dispersed over long distances and usually be long-lived for several years. These species also have certain characteristics that can protect or defend them against herbivores and that can provide multiple recovery tactics. Survivor species on the other hand are species that remain after poor or neglected field management. These species are usually unpalatable or poisonous, proliferate seed poorly and have a week seedbed that is not retained in soil for long periods. Prof Nico Smit reported on bush encroachment being one of the biggest problems in the savannah biome. He suggested that the cost effectiveness of chemical control of invasive bush species should be carefully looked at and managed since it depends on the rate of re-establishment of species and the necessary follow-up control which will result in secondary costs. He warned that landowners should rather do nothing, than do the wrong thing since disturbance may only be a trigger to enhance bush encroachment. He emphasised that the management of bush encroachment is a long-term control strategy and where possible should be seen and be approached as a resource rather than a problem. Dr Pieter Winter from the South African National Biodiversity Institute (SANBI) gave an informative presentation on why it is necessary to identify invasive species correctly. There has to be a knowledge base since invasive biology is dynamic and change over time. The South African National Biodiversity Institute contains various herbarium collections which require constant examination, therefore the expertise of taxonomists should not be overlooked. Dr Seb Rahlao also from Grassroots SANBI gave an overview of the National Status Report on the biological status of invasive plant species. The Alien and Invasive Species Regulations (2014) and the respective lists of invasive species (559 spp.) are available on the website, www.invasives.org.za. These invasive species are categorised according to the National Environmental Management: Biodiversity Act (NEMBA) into four groups (i.e. 1a, 1b, 2 and 3) according to their invasive status. The ideal is to update these lists every six months, however the feasibility is questionable. The National Status Report gives information on the distribution, rate of spread and risk assessments involved of invasive species. Dr Graham Harding elucidated the role of herbicides in invasive alien plant management and stated that chemical control is an essential tool in management strategies. He accentuated the importance of understanding the application and use of the different products registered to be used in controlling various invasive species. It is not realistic to ban chemical control from management strategies, rather use less herbicides, but use it correctly, at the right time and adhere to label recommendations of each product. Dr Helmuth Zimmerman ended the workshop with the exceptional successes with the biological control of invasive Cacti in the north-western grasslands. He gave an overview of the work that has been done to control Opuntia engelmannii with four cochineal species (sap-sucking insects). It was a journey with trial and error, but at the end all the research and hard work paid-off. Biological control cannot eradicate invasive species completely, but the main objective with biological control is to get a balance between the host and the predator. Dr Zimmermann also informed the workshop that new invaders are always on the horizon and gave an update on invaders such as Opuntaelata Harissiatortuposa, Thephrocactus articulates, Cylindropuntia spinosior and C. pallida. Other speakers included Mr. Justin du Toit from Department of Agriculture, Forestry and Fisheries who explored invasive plant management strategies in grassland especially where slangbos [Seriphiumplumosum (syn. Stoebe vulgaris)] and katbos (Asparagus laricinus) were predominant. Mr September 2016 Vol 16 No. 3