Combating Invasive Plants and Animals
North America is being invaded. This invasion is not obvious, but is happening in a ditch or garden near you. It is an invasion of foreign plants and animals. These plants can crowd out native plants by out competing them for resources such as sunlight, nutrients, water, and places to grow. The animals, from insects to mammals like nutria, can wipe out whole ecosystems by taking those resources instead of leaving them for the plants and animals that are supposed to consume or be protected by them. Sometimes they carry diseases that decimate wild populations of a plant or animal.
Invasive plants can be intentionally brought in to the area by humans or they can arrive accidently when they stow away on plants or other materials humans bring in the area. Have you ever been to the airport and seen the United States Department of Agriculture beagles sniffing luggage? They are trained to indicate any time they smell foods or plants in someone’s luggage.
Why is this a problem? Well, those foods or plants may be a problem for native species. They can carry diseases or pests that we do not have here and that native plants are not able to cope with. For example, the Emerald Ash Borer that is devastating ash trees in the Eastern United States and the mid West hitched a ride in something from Asia, got loose, and has killed millions of trees. The economic burden of losing ash trees to a foreign pest can cause businesses such as saw mills and lumber yards to close. In fact, states and the federal government are trying desperately to save not just these trees but the whole ecosystem that lives in and around them. Imagine never being able to buy anything made from ash trees again. That can become a reality if this invasive pest is not stopped.
Another example is kudzu. Unlike the Emerald Ash Borer, it was brought here intentionally. Resource managers advocated planting it along roads and pond dams to control erosion. Unfortunately, it grows very rapidly and covers native plants. Native plants are smothered by kudzu and cannot get the sunlight they need. It resembles trying to breathe with a pillow over your head.
Invasive species cost the world approximately 1.5 trillion dollars a year. This is five percent of the global economy. Think of the things that money could go toward if it were not spent this way.
How can you help? Many invasive plants were brought here by well-meaning people for their garden. For example, multiflora rose is often called wild rose. It is not really wild, but was planted on purpose by gardeners in the 1700s in this country. It was planted as an ornamental and as a living fence to keep livestock in, or out. It was also planted for erosion control.
Not only does multiflora rose grow into a huge briar patch and crowd out anything, flora or fauna, in the way, it carries a disease to other roses. Rose rosette disease is a virus that is carried by a microscopic mite that feeds on multiflora rose and then on domestic roses. It carries the disease where ever it feeds. Because it is a virus, there is no cure for rose rosette disease. Roses that have been infected have to be dug up and destroyed to stop the spread of the disease. Entire rose gardens have had to be destroyed because of a microscopic mite brought in on some roses in the 1700s.
Before you plant a non-native species of plant, check around. Both the federal government and state governments, or provincial governments, have hit lists of invasive species that should not be planted or grown in their areas.
How do you get rid of invasive species? There are three general ways to eliminate any plant: mechanical, chemical, and biological. Each species can generally be removed by any of the three methods. However, there is usually one preferred method to remove a particular species with minimal impact to other plants and animals in the area.
Mechanical control is physically removing the species of plant from the environment. Because it does not require special training or licensing, mechanical control is usually the method tried first. It is the most labor intensive of the three removal methods. It disrupts the environment the most. To mechanically remove a species, it has to be dug up and destroyed. This is difficult because for most invasive species, even a piece of a root left behind can grow into a new plant. For example, tilling a pasture to get rid of Bermuda grass essentially plants all the pieces, which re-infest the area. In many cases, the Bermuda comes back stronger than ever. It is best to use this method of removal in the early spring, when plants are smaller and the soil is moist. This makes removing the plants easier.
Chemical control kills invasive species by spraying them with herbicide or growth inhibitors to keep the plant from growing. It generally requires a permit. Care must also be taken to insure that the chemical control does not destroy anything but the targeted species.
Almost all chemical control can be achieved by using one of two chemicals. Glyphosate is a non-selective herbicide. It kills most plants. The chemical is applied to the leaves of the plant while the plant is still growing. It goes down the stems to the roots with the results of photosynthesis and attacks the plant’s root system. Care must be taken to not spray a plant you want and kill it as well as the invasive species.
Triclopyr is the other herbicide that can kill brush. It does not injure monocots such as grass, lilies, orchids, etc. The effects associated with auxins like triclopyr, help set them apart from other downwardly mobile herbicides. Bending and twisting of leaves and stems is evident almost immediately after application. Delayed symptom development includes root formation on dicot stems; misshapened leaves, stems, and flowers; and abnormal roots. Like glyphosate, care must be taken to keep triclopyr off non-target species.
Chemical controls may have a residual effect or may only kill when actually applied to the plant. Glyphosate generally has no residual effect. It can, however, be combined with a plant growth regulator for longer control of the invasive species.
Biological control uses other plants, insect and other pests, and plant specific diseases to control invasive plants. These usually originate in the plant’s original location and have evolved to keep that plant in check there. Care must be taken not to release a biological control that will effect anything but the target species or you will end up with another problem in that ecosystem. It is usually used in remote areas where other control methods are not economically feasible. The jury is still out on whether biological control helps or harms the area. It is irreversible, so all the possible effects of biological control must be investigated before using it.
Before purchasing seeds or plants for your garden or landscape, take the time to study the lists of invasive species for your area. You can usually find a related but not invasive species to use if the desired species is considered invasive. Often the native species will resemble its cousin and help you achieve the desired effect in your landscape.