Impact of weeds

Weeds in Australia

About weeds

Impact of weeds

Weeds are one of the major threats to the natural environment. They are destroying native habitats, threatening native plants and animals and choking our natural systems including rivers and forests.

Directly or indirectly, all Australians are affected by weeds. Weeds reduce farm and forest productivity, invade crops, smother pastures and some can harm livestock. Land and water managers incur material and labour costs to control weeds — these costs are passed on to the Australian public through higher prices for produce.

The economic cost of weeds

Weeds reduce the quantity and quality of Australia’s agricultural, horticultural and forestry products, affecting both industry and consumers. It is estimated that weeds cost Australian farmers around $1.5 billion a year in weed control activities and a further $2.5 billion a year in lost agricultural production. The real cost of weeds to the environment is difficult to calculate, however it is expected that the cost would be similar to, if not greater than, that estimated for agricultural industries.

The CRC for Australian Weed Management has produced a series of technical papers evaluating the cost of weeds to the Australian environment and agricultural sectors.

The impact of weeds on the environment

Weeds are one of the major threats to Australia’s natural environment. Major weed invasions change the natural diversity and balance of ecological communities. These changes threaten the survival of many plants and animals because the weeds compete with native plants for space, nutrients and sunlight.

Almost all of Australia’s native vegetation communities have been invaded, or are vulnerable to invasion by exotic species that could result in changes to the structure, species composition, fire frequency and abundance of native communities.

Nationally, invasive plants continue to invade the land with exotic species accounting for about 15% of flora. About one-quarter of them are either serious environmental weeds or have the potential to be serious weeds.

Weeds may out-compete native plants because:

  • they may not be affected by the pests or diseases that would normally control them in their natural habitats
  • the disturbed environment provides different conditions that better suit the invading weed.

As a result the weed may:

  • grow faster than native plants and successfully compete for available nutrients, water, space and sunlight
  • reduce natural diversity by smothering native plants or preventing them from growing back after clearing, fire or other disturbance
  • replace the native plants that animals use for shelter, food and nesting.

Weeds are often excellent at surviving and reproducing in disturbed environments and are often the first species to colonise and dominate in these conditions.

Weeds in the ocean spread over wide areas in a very short time. Introduced seaweeds came to Australia in the early 1980s in the ballast water of ships. They are now invading marine environments along the coast of south-eastern Australia.

The impact of weeds on agriculture

Weeds reduce farm and forest productivity, they invade crops, smother pastures and in some cases can harm livestock. They aggressively compete for water, nutrients and sunlight, resulting in reduced crop yield and poor crop quality. For example, prickle bushes such as Gorse, Blackberries, Prickly Acacia, Parkinsonia and Mesquite can invade vast areas of grazing land preventing productive use of that land.

Weeds contaminate produce, for example:

  • Burrs in wool contaminate fleeces
  • Grain milled with Saffron Thistle or Amsinckia results in discoloured flour
  • Animals that eat specific weeds, such as wild garlic, produce tainted milk and meat
  • Spines on fruit of Caltrop and Spiny Emex can damage the feet of stock animals
  • Paterson’s Curse irritates the udders of dairy cows and can kill horses
  • Hemlock can be lethal to both stock and people.

Weeds can also affect the operation of farm machinery.

Farmers spend a large amount of time and money managing weeds. Despite control efforts, a recent Australian Bureau of Statistics survey of issues facing the agriculture industry found that weeds were the most commonly reported natural resource management issue affecting landowners. Weed-related issues affected 73% of Australian agricultural establishments during 2004-05. This compares to 46% of farmers reporting soil and land issues and 38% reporting water issues.

The impact of weeds on human health

Weeds can also cause human health problems. Many common weeds such as Parthenium Weed, Ragweed, Rye Grass and Privet cause asthma and other respiratory problems, especially in children. Some weeds can also cause skin irritation and some are poisonous.

Some water weeds such as Water Hyacinth (Eichhornia crassipes) and Cabomba (Cabomba caroliniana) can affect the quality of our drinking water if infestations are not managed within water supply dams.

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There are no common characteristics of a poison or harmful weed that would help distinguish them. But as a general rule, plants with a bitter taste, unusual smell, milky sap or red berries may be poisonous with some plants having poisonous roots and bulbs.

Further information

  • Health direct: Stinging plants
  • Fact sheet: Poisonous plants : from The Sydney Children’s Hospitals Network
  • Raising Children Network: Dangerous plants

You may also wish to contact the Asthma Foundation in your state or territory for information on creating low allergy gardens.

Marble Khrushch: what harm to horticultural crops

What is a Pest?

We know that certain insects can feed on the blood of people or other vertebrate animals, and can transmit diseases that are very serious health concerns. These are pests. Nearly every kind of plant in nature is food to one insect or another. When insects feed on plants that we as humans dont want them to, they become pests. Agricultural crops and horticultural plants are consumed by a number of different insects and are at risk from the time the seed is planted until the crop is harvested, stored, or consumed. When insects compete for the same foods as humans, we consider them pests. If insects sting, bite, annoy, contaminate, or make life less pleasurable in any way, people consider them pests. Insect pests may damage homes, clothing, or other products that we make, store, or use. Insects that harm us or our animals, destroy our foods, or damage our buildings, structures, or the materials we producein short, compete with humans in any wayare called pests.


The Southern Nursery Integrated Pest Management (SNIPM) working group comprises a group of extension professionals from Florida, Georgia, Kentucky, North Carolina, South Carolina, Tennessee, and Virginia representing Entomology, Horticulture, and Plant Pathology are collaborating on a multi-state nursery crops project that includes the development of a Crop Profile and a Pest Management Strategic Plan (CP/PMSP).

Resources for Growers and Landscapers

IPM Books for Southeastern Nursery Growers

«IPM for Shrubs in Southeastern US Nursery Production: Volume II» please visit the IPM Shrub Book II or iBooks.

For more information «IPM for Shrubs in Southeastern US Nursery Production: Volume I» please visit the IPM Shrub Book or iBooks.

For more information about «IPM for Select Deciduous Trees in Southeastern US Nursery Production» please visit the IPM Tree Book or iBooks.

Pest Control Guide for Nursery Crops and Landscape Plantings

This pest control guide for Southeastern US nursery crops and landscape plantings was released in 2017. In it, you will find up to date information about pest control products used in nursery crops, greenhouse crops and ornamental landscape plantings. The information provided in this publication is, as much as possible, up to date at the time of publication. However, product registrations can differ between states and labels can change. Thus, this information is intended as a guide to aid in pest control decision-making and not a substitute for reading and following the directions and guidelines on the pesticide label. Download your copy of the 2017 Southeastern U.S. Pest Control Guide for Nursery Crops and Landscape Plantings today.

2017 Fungicide efficacy table for Ornamental Crops Released

SNIPM associated Extension specialists at University of Kentucky (Nicole Gauthier), University of Georgia (Jean Williams-Woodward), and University of Tennessee (Alan Windham), along with a past Extension specialists from Cal Poly (Kelly Ivors) just released the resource Relative Effectiveness of Various Chemicals for Disease Control of Ornamental Plants.

IPMPro and IPMLite apps for iPhone, iPad, and Android!

To learn about IPMPro or for user support please visit IPMPro app. To learn about IPMLite or for user support please visit IPMLite app.

IPM Blog for Southeastern Nursery Growers

For news alerts and tips from Southeastern university research and extension specialists visit [1].

Mission Statement

The Southern Nursery IPM (SNIPM) Working Group is a collaboration among research and Extension professionals to provide timely integrated pest management (IPM) information to commercial horticulture growers, green industry professionals and extension educators; to identify and solve nursery-based IPM problems; develop technology to encourage use of and improve the efficacy of IPM practices and advocate the adoption and retention of IPM principles andpractices to commercial growers and policy makers.


Name University Department State Contact Info.
Craig Adkins NC State University Area Specialized Agent, Agriculture — Commercial Horticulture NC Contact Craig
Fulya Baysal-Gurel Tennessee State University Otis Floyd Nursery Research Center TN Contact Fulya
S. Kristine Braman University of Georgia Department of Entomology, Griffin GA Contact Kristine
Matthew Chappell University of Georgia Horticulture Department GA Contact Matthew
Juang-Horng (JC) Chong Clemson University School of Agricultural, Forest, and Environmental Science

Pee Dee Research and Education Center

SC Contact JC Adam Dale University of Florida Entomology and Nematology Department FL Contact Adam Johanna Del Castillo-Múnera University of Maryland Dept. Plant Sciences and Landscape Architecture MD Contact Johanna Jeffrey F. Derr Virginia Tech Department of Plant Pathology, Physiology, & Weed Science VA Contact Jeff Winston C. Dunwell University of Kentucky Department of Horticulture KY Contact Win Steven Frank NC State University Department of Entomology NC Contact Steven Amy Fulcher University of Tennessee Department of Plant Sciences TN Contact Amy Frank Hale The University of Tennessee Entomology and Plant Pathology Department TN Contact Frank Francesca Peduto Hand The Ohio State University Ornamental/Turf Pathology OH Contact Francesca Bill Klingeman The University of Tennessee Department of Plant Sciences TN Contact Bill Gary Knox The University of Florida Environmental Horticulture Department

North Florida Research and Education Center

FL Contact Gary Anthony LeBude NC State University Horticultural Science,

Mountain Horticultural Crops Research & Extension

NC Contact Anthony Christopher Marble University of Florida, Environmental Horticulture Department,

Mid-Florida Research & Education Center

FL Contact Chris Joe Neal NC State University Department of Horticultural Sciences NC Contact Joe Erfan Vafaie Texas A&M University AgriLife Research and Extension Center — IPM TX Contact Erfan Nicole Ward Gauthier University of Kentucky Department of Plant Pathology KY Contact Nicole Sarah White Clemson University School of Agricultural, Forest, and Environmental Science SC Contact Sarah Jean Williams-Woodward University of Georgia Department of Plant Pathology GA Contact Jean Alan Windham The University of Tennessee Entomology and Plant Pathology Department TN Contact Alan



Nursery crop production (both field and container) of ornamental trees and shrubs, is an important sector of US agriculture, especially in the southeastern United States. Ornamental plants are the second most valuable crop in the United States with a market value of $14.7 billion in 2002 (USDA, 2002). More recent state agricultural statistics indicate that the nursery and greenhouse industry is valued at $889,693,000 in North Carolina and at $316,000,000 for nursery crops (excluding greenhouse crops) in Georgia (Boatright and McKissick, 2008; NCDA, 2007b; USDA, 2002). Additionally, nursery crops ranked 1st and 5th among crops for NC and GA, respectively. Collectively, nursery production in GA, KY, NC, SC, and TN represent over one billion dollars in farm gate values annually. Nurseries in these southeastern states employ tens of thousands of workers.

2011 Survey

A regional group of Extension specialists from TN, GA, NC, SC, & KY surveyed current pest (insect, disease, & weed) management practices and current pest priorities of growers in southeastern, wholesale, ornamental nurseries. Our efforts have been funded by the Southern Region Integrated Pest Management Center (SRIPMC) and supported by each cooperating state’s nursery and landscape trade organization.


Conducted 30-31 July 2009 at the Mountain Horticulture Research and Extension Center (MHREC) in Mills River, NC. Nursery crop producers from five states (GA, KY, NC, SC, and TN) were identified and contacted about participating in an effort to identify pest priorities for nursery production. Growers ranked weed, disease, and insects pests prior to meeting as a focus group. Nursery crop growers and University personnel met over a 2 day period to discuss pest problems of trees and shrubs in container and field production. The group further prioritized insect, disease, and weed pests and identified regulatory,extension, and research needs.

Pest Management Strategic Plan

Pest Management Strategic Plans (PMSPs) are widely recognized as a conduit for communication from growers and other IPM practitioners to regulators and granting agencies. These documents give a realistic view of pest management issues and strategies used in the field and provide a forum to set meaningful research, regulatory, and educational priorities. Pest Management Strategic Plans (PMSPs) are developed by growers or other stakeholders to identify their pest management needs. Each plan has a state, region or national focus. The plans take a pest-by-pest approach to identifying the current management practices (chemical and non-chemical) and those under development. Plans also state priorities for research, regulatory activity, and education/training programs needed for transition to alternative pest management practices.

Plant Sciences

The Department of Plant Sciences along with the fully integrated Crop Development Centre (CDC), provide a truly unique experience to students by offering teaching and research programs focusing on the physiology, development management and production of field and horticultural crops on the Canadian prairies and the management of non-arable lands.

We are the only plant sciences department in Canada capable of offering such a diverse experience in plant studies. Our close cooperation between the department and other research institutions on campus, such as the Plant Biotechnology Institute of the National Research Council, the Agriculture and Agri-food Canada Research Station, the Protein, Oil and Starch (POS) Pilot Plant and the Canadian Light Source allows graduate students to participate in interdisciplinary research.


Sustainable Systems

Agronomy of Horticulture and Field Crops

The agronomy of horticultural/medicinal crops includes research on crop improvement through standard breeding and molecular techniques, micro-climate modification, integrated pest management and various other aspects of the agronomy of potatoes, vegetable crops, spice crops and medicinal plants.

Agronomy of field crops focuses on proper crop & weed management systems as well as non-herbicidal options of weed control.

Principal Investigators: Steve Shirtliffe (field crops), Kate Congreves (horticultural crops)

Applied Plant Ecology

Interactions between plants and their environment are studied at levels from molecular, individuals, populations, communities, and landscapes. Studies are conducted in a wide range of ecosystems including grasslands, forests, wetlands, and arctic tundra. Past and current research projects include plant species and genetic diversity, plant responses to climate change, vegetation dynamics in ecotones, ecosystem carbon balance, greenhouse gas emissions, conservation of species at risk, restoration ecology, fire ecology, and primary productions.

Organic Production Systems

Determining best organic weed control systems through the use of tillage, cultural methods and crop rotations are studied in both field and horticultural crops.

Principal Investigators: Steve Shirtliffe (field crops)

Nutrient management and biogeochemistry

Molecular Genetics and Crop Improvement

Research and training is focused on preparing students for a career in plant breeding, molecular genetics and genomics, and related disciplines. Research programs focus on training in classical and molecular breeding of field and horticultural crops with emphasis on deciphering the genetic basis of desirable phenotypes. Research is mulitdisciplinary, with integrated programs in plant pathology, genomics, biochemistry, physiology and agronomy, ecology and biodiversity, statistics and bioinformatics and crop end-use functionality. Unique to the Department of Plant Sciences is the full integration of the Crop Development Centre (CDC), which allows students the opportunity to focus on one of several crop species with economic value at the local and international level.

Breeding, Genetics and Management of Pulse Crops

Principal Investigators: Bunyamin Tar’an (chickpea), Kirstin Bett (dry bean) Bert Vandenberg (lentil and fababean), Tom Warkentin (field pea and soybean)

Breeding, Genetics and Management of Cereal Crops

Principal Investigators: Curtis Pozniak (durum wheat), Pierre Hucl (spring wheat, specialty wheat, canaryseed), Brian Fowler (winter wheat), Aaron Beattie (barley and oat)

Breeding, Genetics and Management of Oil Seed Crops

Principal Investigators: Helen Booker (flax)

Breeding, Genetics, and Management of Horticultural Crops

Principal Investigators: Bob Bors (fruit crops)

Breeding, Genetics and Management of Forage Crops
Molecular Genetics and Genomics of Crop Plants
Molecular Genetics and Genomics of Asexual Plants

Crop Protection

Plant Pathology

Plant Pathology research focuses on cereal, horticultural, and pulse crops and covers a variety of disciplines including epidemiology, fungicide research, integrated disease management, histology of infection processes, genetics of host-pathogen interactions, variation in pathogen populations, and breeding for disease resistance.

Principal Investigators: Randy Kutcher (cereal and flax crop pathology), Sabine Banniza (pulse crop pathology)

Weed Management

Weed Science research encompasses conventional, zero-till and organic cropping systems, integrated weed management strategies for various crops and weed biology/ecology. Herbicide studies concentrate on developing effective control measures for problem weeds in field and special crops, determining soil persistence and safe re-cropping intervals and improving herbicide efficacy through application technology.

Principal Investigators: Steve Shirtliffe (agonomy and weed ecology), Chris Willenborg (weed control)


Entomology research focuses on insects and arthropods that benefit or harm humans, primarily through their effects on crops. Research includes Integrated Pest Management (IPM), pollination biology, vector biology, biological control, and evaluation of breeding material for resistant and tolerance to insects.

Environmental Physiology

Abiotic Stress

Research encompasses plant responses and adaptation to environmental stressors including low temperature, early frost, salt, drought and heat stress from ecological to molecular levels.

Physiology of Field Crops and Native Plants

The mechanisms of field crop plants grown on the Canadian Prairies as well as plant from the Canadian Prairies and the Boreal Forest are studied with a focus on the regeneration using modeling approaches.

Field Crop physiology research focuses on growth and yield response to environmental factors and yield formation processes in field crops

Native plant past and current projects include seedbed ecology of grassland and forest species, dormancy induction and acclimatation of deciduous trees, using thermal and hydrothermal time to study seed germination, spatial variability in plant regeneration, germination of seeds in response to climate change, and abiotic stresses.

Principal Investigators: Yuguang Bai (native plants), Rosalind Bueckert (field crops)

Crop Adaptation

Research on the genetics and mechanisms of traits involved in plant adaptation provides the scientific knowledge base essential for informed crop breeding programs. Day-length sensitivity is an important factor in breeding crop cultivars, and early maturity (earliness) is an important trait in many regions of the world. In Canada, earliness is required due to the short growing season. Earliness may also protect the crop from various biotic and abiotic stresses such as diseases, heat, drought and frost.

Characterization of early maturity (earliness) in crop plants allows plant breeders to combine this trait with other novel genes and create varieties targeted for different agronomic environments and management practices. This will improve overall productivity of the crop plant and lead to further knowledge on the genetic potential of crop plants for adaptation to environmental limitations.

Crop Quality

Crop Quality Genomics

Crop quality research focuses on using genetically modify carbohydrates and other bioactive ingredients in cereal and pulses to diversify their utilization. Research objectives are to improve grain quality (cereals and pulses) so that grain carbohydrates in addition to providing calories, grain based products improve gut health and reduce incidence of obesity and cardiovascular diseases.

Lipids Quality and Utilization

Research focuses on strengthening the utilization of plant-based oils, fats, waxes, and other compunds derived from the fractionation of lipids from seed crops in Saskatchewan. Long-term results of the research will help to enhance the value-added processing of crops grown in Saskatchewan.

Research activities include the assessment of quality and composition of oils from Saskatchewan crops and the assessment of fractionation of functional lipids and essential components from plant oils. Activities also investigates the extraction, clarification and functionality of plant oils.


Graduate Studies

Department of Plant Sciences along with the Crop Development Centre has the mission of teaching, research and outreach relating to the development, production and management of Field and Horticultural crops on the Canadian Prairies and the management of non-arable lands. The Crop Development Centre (CDC) is a “Centre of Excellence” field crop breeding organization that is fully integrated within the department.

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