Non-Native Invasive Plants in Virginia s Forests

1. Non-Native Invasive Plants in Virginia’s Forests Chris Asaro Virginia Dept. Forestry Of the alien plant species introduced to the United States that have escaped cultivation, half were introduced for horticultural uses and others arrived accidentally in seed mixes, packaging materials, ships ballast, and by other means. They now infest more than 100 million acres. The Virginia Department of Conservation's Division of Natural Heritage and the Virginia Native Plant Society have identified 115 invasive alien plant species that threaten or potentially threaten natural areas, parks, and other protected lands in Virginia. Of the alien plant species introduced to the United States that have escaped cultivation, half were introduced for horticultural uses and others arrived accidentally in seed mixes, packaging materials, ships ballast, and by other means. They now infest more than 100 million acres. The Virginia Department of Conservation's Division of Natural Heritage and the Virginia Native Plant Society have identified 115 invasive alien plant species that threaten or potentially threaten natural areas, parks, and other protected lands in Virginia.

2. Weeds Gone Wild (NPS): “Invasive non-native organisms are one of the greatest threats to the natural ecosystems of the US and are destroying America’s natural history and identity”. “…displacing native plant and animal species, and degrading our nation’s unique and diverse biological resources.” Aggressive invaders reduce the amount of light, water, nutrients and space available to native species, alter hydrological patterns, soil chemistry, moisture-holding capacity, and erodibility, and change fire regimes. Some exotics are capable of hybridizing with native plant relatives, resulting in unnatural changes to a plant's genetic makeup. Others have been found to harbor plant pathogens that can affect both native and non-native plants, including ornamentals. Still others contain toxins that may be lethal to certain animals. For example, garlic mustard has been found to contain compounds that are lethal to a native butterfly species.  Aggressive invaders reduce the amount of light, water, nutrients and space available to native species, alter hydrological patterns, soil chemistry, moisture-holding capacity, and erodibility, and change fire regimes. Some exotics are capable of hybridizing with native plant relatives, resulting in unnatural changes to a plant's genetic makeup. Others have been found to harbor plant pathogens that can affect both native and non-native plants, including ornamentals. Still others contain toxins that may be lethal to certain animals. For example, garlic mustard has been found to contain compounds that are lethal to a native butterfly species. 

3. Jim Miller (USFS): “Invasions of nonnative plants into forests of the Southern United States continue to go unchecked and unmonitored”. They are “increasingly eroding forest productivity, hindering forest use and management activities, and degrading diversity and wildlife habitat”. Exotic organisms have been referred to as biological pollution. In some cases, exotic plant invaders are driving our rarest species closer to extinction. According to the U.S. Fish and Wildlife Service, an estimated 42% of the nation's endangered and threatened species have declined as a result of encroaching exotic plants and animals. Exotic organisms have been referred to as biological pollution. In some cases, exotic plant invaders are driving our rarest species closer to extinction. According to the U.S. Fish and Wildlife Service, an estimated 42% of the nation's endangered and threatened species have declined as a result of encroaching exotic plants and animals.

4. One study estimates that the total costs of invasive species in the United States amount to more than $100 billion each year. Another study estimated that from 1901 to 1991, economic losses in the U.S. caused by 15 invasive plant species (not including agricultural weeds) were $603 million. Introductions of exotic plants continue today, and are increasing due to an exploding human population, increased international travel, and the intentional and accidental movement of large numbers of species between continents as a result of expanded international trade.Another study estimated that from 1901 to 1991, economic losses in the U.S. caused by 15 invasive plant species (not including agricultural weeds) were $603 million. Introductions of exotic plants continue today, and are increasing due to an exploding human population, increased international travel, and the intentional and accidental movement of large numbers of species between continents as a result of expanded international trade.

5. The meaning of words Alien species are also known as exotic, non-native, or nonindigenous. Intentionally or accidentally introduced by human activity into a region in which they did not evolve. Many (like wheat, soybeans, and tulips) are well known and economically important in agriculture and horticulture. Most, whether plant or animal, do not become established outside of cultivation or, if they do, they usually have few impacts on natural communities. Native Range. Every species has a home in some part of the world, where it has existed for thousands of years in balance with natural forces and influences like climate, storms, moisture, fire, soils and species interactions. A native (indigenous) species is one that occurs in a particular region, ecosystem, and habitat without direct or indirect human actions. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.   Organisms are considered non-native (alien, exotic, foreign, introduced, non-indigenous) when they occur in locations beyond their known historical natural ranges. Non-native can refer to species brought in from other continents, regions, ecosystems and even other habitats. Species exotic to the U.S. include those transported from Europe, Asia, Africa, South America, Australia and other parts of the world. Many introduced plants have become naturalized across the continent and some are replacing North American native plant species. These naturalized plants, how ever much a part of our current landscapes and ecosystems, are nonetheless exotic, since they were moved here by people rather than by natural means. Invasiveness. The most important aspect of an alien plant is how it responds to a new environment. An invasive species is one that displays rapid growth and spread, allowing it to establish over large areas. Free from the array of natural controls present in their native range (herbivores, parasites, insects, and diseases), they may experience rapid and unrestricted growth in new environments. Invasiveness is enhanced by features such as strong vegetative growth, abundant seed production, high seed germination rate, long-lived seeds, and rapid maturation to a sexually reproductive (seed-producing) stage.  Invasive plants reproduce rapidly, either vegetatively or by seed. Their phenomenal growth allows them to overwhelm and displace existing vegetation and form dense one-species stands.  Not all exotic species are considered harmful. For example, a small number of non-invasive alien plants (e.g., corn, wheat, oats) form the basis of our agricultural industry and pose little to no threat to our natural ecosystems. However, each alien plant is one less native host plant for our native insects, vertebrates and other organisms that are dependent upon them.  The term weed is a subjective word used to describe any plant considered to be "out of place." In other words, weeds can include native and non-native plants alike, growing wherever someone wishes they weren't. Invasive exotic plants of natural ecosystems are often referred to as natural areas weeds. Biodiversity. Biodiversity is, simply put, all life on earth, even that which has yet to be discovered. More specifically, it includes the millions* of diverse species, from bacteria to whales, that share the earth's lands and waters with us. Each year, many thousands of species are being extinguished as a result of human activities, such as habitat destruction and exotic species introductions.  The term noxious is a legal designation used specifically for plant species that have been determined to be major pests of agricultural ecosystems and are subject, by law, to certain restrictions. The U.S. Department of Agriculture regulates noxious weeds. Alien species are also known as exotic, non-native, or nonindigenous. Intentionally or accidentally introduced by human activity into a region in which they did not evolve. Many (like wheat, soybeans, and tulips) are well known and economically important in agriculture and horticulture. Most, whether plant or animal, do not become established outside of cultivation or, if they do, they usually have few impacts on natural communities. Native Range. Every species has a home in some part of the world, where it has existed for thousands of years in balance with natural forces and influences like climate, storms, moisture, fire, soils and species interactions. A native (indigenous) species is one that occurs in a particular region, ecosystem, and habitat without direct or indirect human actions. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.   Organisms are considered non-native (alien, exotic, foreign, introduced, non-indigenous) when they occur in locations beyond their known historical natural ranges. Non-native can refer to species brought in from other continents, regions, ecosystems and even other habitats. Species exotic to the U.S. include those transported from Europe, Asia, Africa, South America, Australia and other parts of the world. Many introduced plants have become naturalized across the continent and some are replacing North American native plant species. These naturalized plants, how ever much a part of our current landscapes and ecosystems, are nonetheless exotic, since they were moved here by people rather than by natural means. Invasiveness. The most important aspect of an alien plant is how it responds to a new environment. An invasive species is one that displays rapid growth and spread, allowing it to establish over large areas. Free from the array of natural controls present in their native range (herbivores, parasites, insects, and diseases), they may experience rapid and unrestricted growth in new environments. Invasiveness is enhanced by features such as strong vegetative growth, abundant seed production, high seed germination rate, long-lived seeds, and rapid maturation to a sexually reproductive (seed-producing) stage.  Invasive plants reproduce rapidly, either vegetatively or by seed. Their phenomenal growth allows them to overwhelm and displace existing vegetation and form dense one-species stands.  Not all exotic species are considered harmful. For example, a small number of non-invasive alien plants (e.g., corn, wheat, oats) form the basis of our agricultural industry and pose little to no threat to our natural ecosystems. However, each alien plant is one less native host plant for our native insects, vertebrates and other organisms that are dependent upon them.  The term weed is a subjective word used to describe any plant considered to be "out of place." In other words, weeds can include native and non-native plants alike, growing wherever someone wishes they weren't. Invasive exotic plants of natural ecosystems are often referred to as natural areas weeds. Biodiversity. Biodiversity is, simply put, all life on earth, even that which has yet to be discovered. More specifically, it includes the millions* of diverse species, from bacteria to whales, that share the earth's lands and waters with us. Each year, many thousands of species are being extinguished as a result of human activities, such as habitat destruction and exotic species introductions.  The term noxious is a legal designation used specifically for plant species that have been determined to be major pests of agricultural ecosystems and are subject, by law, to certain restrictions. The U.S. Department of Agriculture regulates noxious weeds.

6. Invasive Species: Definition 1) A species that is non-native (or alien) to the ecosystem under consideration, such as the Southeast and…… 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112, signed February 3, 1999 by President Clinton)

7. Non-native Invasive Plant Impacts Limit or stop productive land management and regeneration of forests and grasslands Displace and permanently decrease biodiversity and wildlife habitat Alter vital ecological processes such as soil formation, watershed function, and pollination of native plants Limit land access for recreation such as hiking, fishing, hunting, and bird watching

8. NNIP Impacts (cont’d) Produce overabundant pollen that causes widespread allergenic reaction in humans Present extreme fire hazards Can be poisonous to humans and livestock Harbor plant diseases Cause psychological anxiety through a sense of the inability to control our surroundings (Miller et al., 2010)

9. NNIP: Formula for Success Early introductions, leading to long periods of spread, hybridization and adaptation Rapid early growth rates Few natural enemies Abundant seed production at young age Seed easily spread by wind, water, wildlife Seed viable in soil for 1 year to decades Strong re-sprouting capabilities following topkill

10. NNIP: Formula for Success Capability to establish and spread in disturbed sites “Set and wait’ strategy until conditions are suitable Broad tolerance to shade, drought, flooding, and soil conditions Dense leaf areas, often evergreen, leaf out early and shed leaves later Allelopathy Alter soil chemistry and microfauna to better suit them

11. Many invasive weeds are evergreen or among the first to leaf out in spring and last to drop leaves in fall

12. Some weeds thrive in relatively shaded, forested settings

13. Without some intervention, invasive weeds will continue to aggressively take over, particularly on small forested parcels and disturbed areas

14. NNIP Management Considerations Long term plans for the site Need for selectivity of control Intensity of target plant(s) infestation Importance of timing for control Type and amount of labor available Cost

15. Important Elements of an NNIP Management Program Make a Plan Prevent Entry and Spread Make a map of control locations Eradicate, control or contain Monitor Rehabilitate, restore, or reclaim treated sites Persistence! Timeline for managing older infestations could be 5-10 years

16. NNIP Management Strategies Use The Search, Survey, Inventory, Monitor and Surveillance (SSIMS) Method

17. NNIP Control Strategies & Tactics Herbicides Manual – hand tools Mechanical – equipment, machinery Cultural – burning, planting, seeding, water level manipulation, grazing Biological – import insect herbivore or pathogen specific to target plant Mulching or solarization Utilization Public education Avoid distribution/selling/planting

18. Phases of Weed Invasion and Priorities for Action at Each Phase

19. Decision Table for Prioritizing Invasive Weed Mgmt. Efforts

20. VA Exotic Invasive (Forest) Weeds Top 10 List 1. Tree-of-Heaven 2. Japanese honeysuckle 3. Oriental bittersweet 4. kudzu 5. autumn olive 6. multiflora rose 7. Chinese privet 8. garlic mustard 9. Chinese lespedeza 10. Japanese stiltgrass