Herbicides to Kill Unwanted Wisteria
Chinese wisteria and Japanese wisteria are introduced ornamental vines that have become invasive in much of the Eastern United States. While they do have a place within the garden setting, their aggressive growth habits and prolific reproductive abilities can make them a threat to native species. With this in mind, it may become necessary to eradicate Chinese and Japanese wisteria in certain environments. This can be effectively accomplished with herbicides.
Asian wisterias were introduced into the United States as ornamental plants in the early 1800s. These escaped from their traditional role as a garden plant and now they are considered an invasive species. The plants grow quickly and rampantly, often growing into large trees and establishing themselves within the tree canopy. As the wisteria grows, it can block out sunlight from the tree. The vine can also girdle the host tree, eventually killing it.
Types of Herbicides
Herbicides offer a viable option to deal with wisteria infestations. Several different herbicides are effective and include picloram, triclopyr, glyphosate, imazapyr and clopyralid. All of these herbicides provide effective treatment against wisteria, offering better than 90% control of the plant 12 months after initial treatment.
Picloram, available under the names Tordon, Grazon and Pathway, is often used for the control of woody plants, including wisteria. It is also effective against most annual and perennial broadleaf plants without affecting conifers or grasses. It can be sprayed on the foliage, injected into the plant or applied to cut surfaces.
Triclopyr, sold as Garlon 4 and Remedy, is relatively selective, affecting mainly woody plants such as wisteria as well as some broadleaf plants while leaving grasses and conifers intact. It can also be used in foliar spraying, injection or cut stump applications.
Glyphosate is commonly sold under the brand names Roundup, Rodeo and Accord. This herbicide is broad-spectrum and nonselective. Most plants are susceptible to glyphosate, including wisteria. It is most often applied as a foliar spray.
Imazapyr, known commercially as Arsenal, is another broad-spectrum herbicide that can be applied by spraying on both pre-emergent and post-emergent growth of wisteria. This herbicide can be used in relatively low volumes.
Clopyralid is sold under the trade names Stringer, Curtail, Transline and Redeem. Clopyralid is more selective than other herbicides. Many types of broadleaf and woody species, including wisteria, can be effectively controlled by this herbicide.
Application and Precautions
All of these herbicides should be mixed according to manufacturer's suggested formulations. Cutting the stem of the wisteria plant near the root and painting the surface of the cut with herbicide will prevent reemergence of the plant and is the preferred method of control. Foliar spraying can be done for large infestations where the stems are relatively inaccessible. To improve the contact time for spray herbicides, a surfactant can be added to the mixture. It is important, prior to treating an affected area, to determine if there are any native species that will be adversely affected by the herbicide being applied. Many herbicides are broad spectrum and will affect a wide variety of plants. Care should be taken to prevent over spray and drift of herbicides to areas beyond those being treated.