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Prepare to be Invaded!, or A Quick Study on Invasive Organisms. What does it mean to be “invasive”?. Exotic (not endemic, or native to an area). But that is simply not enough…. 2) Able to survive and reproduce in the new area. -a distinct breeding population,
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Prepare to be Invaded!, or A Quick Study on Invasive Organisms What does it mean to be “invasive”? • Exotic (not endemic, or native to • an area) But that is simply not enough…
2) Able to survive and reproduce in the new area. -a distinct breeding population, more than just a few random individuals But this is STILL not enough!
3) The population needs to take over another populations niche, or force it out. -Invasives often become a mono- culture, and wreck the ecosystem. -Loss of diversity, loss of habitat, loss of food for other organisms, etc..
Things most invasive species have in common: 1) No natural predators, so nothing to hold the population down. 2) Usually very prolific, reproducing very rapidly. 3) Have characteristics that exclude native species from a habitat.
Some Quick Numbers: $137 BILLION dollars in damage due to invasives every year. 50,000 exotic species (estimated) are released in the US every year. But there is some GOOD news!
The 10% Rule Only 10% of introduced exotics will live at all. -Wrong climate, food availability, etc.. Of the 10% that live, only 10% will actually be able to breed and become invasive. -You need to find a mate and the proper conditions to raise young.
Invasive Organisms in Delaware -There are a number of invasive, non- native organisms that have made Delaware their home. Below is a sample of some of the most invasive, some of which you might think are native organisms.
1) Kudzu vine -Native of Asia, brought to the U.S. to control erosion along river banks and new ditches -infests 2-3 million acres in eastern U.S., with an annual loss of over $50 million due to lost productivity, and cost of control.
2) Nutria: -small wetland mammal, brought from South America for its fur. The fur trade never really took off, now it’s a very bad pest in wetlands. -it eats young shoots and roots, killing marsh plants, destroying wetlands
3) Multiflora Rose: -Native to Asia, brought to U.S. from Japan in the 1800’s. -Used to control erosion along rivers and act as a “living fence”. -Forms dense thickets, crowds out native plants and animals. -Very prolific breeder, makes many seeds, can grow just about anywhere.
4) Gypsy Moth: -introduced to this country from Asia in 1868, accidentally. -voracious eaters, especially fond of oak trees. -is responsible for the general decline in numbers of oaks in forests over the past 100 years.
5) Purple Loosetrife: -Native to Europe/Asia -Introduced in the 1800’s to U.S. -wetland plant, very aggressive competitor for land, nutrients. -crowds out native reeds, cattails. -extremely prolific, one plant can produce over 30,000 seeds.
6) Honeysuckle: -Imported from Japan in 1862 to Long Island, N.Y. -Very tenacious vine, covers and pulls down large trees and shrubs -Often grows in disturbed areas, such as roadsides, and along edges of forests.
7) European Green Crab -Native to Africa/Europe -tolerates a wide variety of conditions -eats many more clams/mussels than native crabs, causing a decrease in numbers of clams. -pushes many other crabs out of the habitat, and takes over (aggressive).
NATIVE Calico Crab INVASIVE European Green Crab
8) Mute Swan: -Native to Europe -introduced to U.S. by European admirers, has shown a great population increase since introduction. -very aggressive, competes with native waterfowl for food and breeding space. -is taking over in many places.
9) European Starling Introduced in 1890 as part of a plan to introduce to the U.S. all birds mentioned in the works of Shakespeare. (12 birds released) Very aggressive, pushes native song birds away From feeders and nesting areas. Highly prolific, they breed in conditions that other birds cannot, and so have a high population. (Estimated at over 200 million in the U.S.)
10) Japanese Beetles Introduced accidentally into New Jersey from Japan in 1916 and is now widespread over the eastern United States. Both the grub and the adult are voracious eaters, and cause widespread damage to trees, shrubs, and grass.
Introduction of Invasive Species 1) Intentional Introduction -for economic purposes (Ex: nutria) -for cultural purposes (Ex: starlings, Asian Shore crabs) -for aesthetic reasons (Honeysuckle, Purple Loosestrife -for misguided environmental projects (Kudzu, Multiflora rose)
2) Accidental Release -Ballast water transfer from foreign areas (Green crab, Zebra Mussel, Comb Jellyfish) -Accidental release of organisms (gypsy moth, “Killer” African bees -Transfer in packing material (European Green Crab to California, Horned Asian Beetle)
Control of Invasives Much of the control of invasive pests relies on the ability to lower the population early on, before the size has grown beyond our capability to handle it. -Once the population has a “foothold”, it is much harder, if not impossible to eliminate.
Control vs. Eradication It may not always be in our best interests to completely eliminate a population of pests. -economics and environmental damage play a role in deciding to eradicate an invasive. -Is the cure better than the problem?
Past a certain point, eradication will be virtually impossible in any case. Usually, by the time the pest is noticed, the ability to eradicate it has been lost. -Especially in marine ecosystems, because of the ability of the organism to go without being noticed until large numbers exist. This makes a good case for close monitoring of critical habitat.
Control of Invasives Population Size Time (months) Ability to Control is lost Point of First Discovery
Success of control depends on a few key factors: • Catching the infestation EARLY, before • population numbers get out of hand. 2) Whether or not the invasive organism is mobile within the environment. 3) How rapidly the invasive can reproduce. -does it reproduce in more than one way? -does it need certain conditions? 4) How vulnerable the invasive is to control. -is it tolerant to pesticides? -will it re-grow if burned?
Control Methods Control Methods can include: 1) No action. This alternative may be chosen if the pest numbers are low enough that they don't interfere with management goals 2) Physical (manual & mechanical) management 3) Cultural management 4) Biological management 5) Chemical management
Mechanical or Physical Management: Mechanical or physical control methods involve using barriers, traps, or physical removal to prevent or reduce pest problems. Tactics may include baited or pheromone traps to capture insects, or cultivation or mowing for weed control.
Cultural management: Cultural practices are a manipulation of the habitat environment to increase pest mortality or reduce rates of pest increase and damage. There are many different cultural practices that can help to reduce pest impact such as selection of pest resistant varieties of crops, mulching, addition of beneficial insect habitat, or other habitat alterations.
Biological Management: Biological control is the deliberate use of the pest's natural enemies - predators, parasites, and pathogens - to reduce the pest population below damage levels.
