Introduction
Evans, C.W., C.T. Bargeron, D.J. Moorhead & G.K. Douce. 2005. Invasive Weeds in Georgia. The Bugwood Network, The University of Georgia.
What is an invasive species? An invasive species is any species (including its seeds, eggs, spores, or other biological material capable of propagation) that is not native to a given ecosystem; and whose presence causes economic or environmental harm or harm to human health. Some of the invasive species in this brochure are already serious pests in Georgia while some are currently just threats and not yet widespread. Twenty of Georgia’s many invasive weeds are highlighted here.
How do invasive species get here? Invasive species are introduced into a new environment, either intentionally or accidentally. Intentional introductions have often been for agricultural or ornamental purposes. Once introduced, they escape from cultivation, or from their aquariums or cages in the case of animals, and become established as viable, self-reproducing populations. Accidental introductions are usually the result of contaminated freight, where individuals or the seeds from invasive species are mixed within normal freight.
Are all exotic species invasive? No, actually only a small percent of the introduced species ever become invasive. However, it is nearly impossible to predict which species will become invasive and new species are being introduced every day. Some species have been introduced for many years before becoming invasive. These are thought to go through a “lag phase” in which their populations grow slowly until they reach a size large enough for the population to explode and become invasive. Chinese privet is a good example of this in the Southeast. Chinese privet has been in the Southeast for many years but until recently its population remained at low numbers. Now it is a serious invasive species, found throughout nearly all of the Southeast.
What type of harm do invasive species cause? Since invasive species are in a new environment, free from the natural predators, parasites, or competitors of their native habitats, they often have very high population sizes. These large populations can out-compete and displace native species, or can reduce wildlife food and habitat. Some also have the potential to disrupt vital ecosystem functions, such as water flow, nutrient cycling, or soil decomposition. Other invasive species cause massive amounts of economic damage to the agricultural industry. They can harm or kill crops, clog equipment, or contaminate produce. Some invasive species can cause direct harm to humans or domestic animals.
What can I do to fight invasive species? The simplest thing anybody can do to help fight invasive species is to Not plant or transmit an invasive species. Check to see if a plant is invasive before planting it. Do not empty aquariums or dump houseplants into the wild. Be sure to clean your shoes and brush off your clothes after being in an area with invasive species. Report any occurrence of invasive species, especially federal noxious weeds, to your local county extension agent. Volunteer with natural resource agencies to control invasive species. Eradicate or control populations of invasive species on your own land. Spread the word; tell your neighbors if you see invasive species on their land. Don’t hesitate! Begin control efforts as soon as you find invasives on your land. Controlling small infestations is more effective and economical than trying to control a well-established, rapidly spreading infestation.
Control recommendations. Several different methods to control invasive species are available. Control methods fall into three main categories: mechanical, chemical, and biological. In many cases a combination of mechanical plus chemical control may be the most effective option.
Mechanical. Mechanical control involves physical removal or destruction of the invasive species. Common techniques include hand pulling, digging, cutting, mowing, and burning. Prescribed fire has been used in a variety of situations to control invasive species. (Before attempting to use prescribed fire check with your local Georgia Forestry Commission office to obtain a permit and weather information.) Repeated mechanical treatments are often necessary to totally eradicate a population. Many invasive species resprout vigorously after being cut and often a viable seed bank is present. Be sure to visit the infestation site every year and remove all new sprouts and seedlings. Continue this until no more individuals have been sighted for several years in a row. This type of control is usually best done early in the year, before seeds are produced. Mechanical control alone may not be practical for large infestations.
Chemical. Chemical control is the use of herbicides to kill individuals of a population. It can be used to effectively control both large and small infestations. Use herbicides carefully. Many herbicides are not selective and will kill all surrounding vegetation or may harm aquatic systems. Before buying, mixing, and use of herbicides, be sure to read and follow label information and wear the appropriate safety gear. Contact your county extension agent for specific recommendations on herbicide use. Trade names do not imply endorsement by the cooperators. Detailed information about chemical control options can be found at www.invasive.org.
Biological. Biological control programs have been initiated for several invasive species in Georgia. Biological control involves using a predator, parasite, or disease that affects the invasive species, either killing it or reducing its competitive advantage.
References
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