Revised April 2003
Kudzu (Pueraria lobata [Willd.] Ohwi.) is one of the most difficult weeds to control in the Southeastern United States. The species was introduced to this country from southeast Asia as early as 1876 (Shurtleff and Aoyagi, 1977). It was initially established as an ornamental, but was used later for erosion control and supplemental cattle grazing. Because of its rapid growth and ability to capture sites at the exclusion of nearly all other plants including trees, it is now widely recognized as a noxious weed. Kudzu has infested an estimated two million acres of land in the South and considerable research has been devoted to developing economical control measures. Overgrazing and repeated mowings have provided effective control in certain situations (see Miller and Edwards, 1983 for details). Recently, herbicide treatments have been developed for this purpose. This report summarizes current guidelines for controlling kudzu with herbicides. It is based on research conducted by Dr. Jim Miller, a research forester for the USDA Forest Service, George W. Andrews Forestry Sciences Laboratory, Auburn, Alabama.
A Commitment of Time and Money
Lands infested with kudzu are generally good for only one purpose — growing kudzu. In order to convert kudzu sites to productive forest or cropland, total eradication is a necessity. The landowner should be warned that this involves a long-term commitment in time and money. Because of its rapid growth (up to 60 feet per year), a single surviving kudzu plant can spread and re-infest a site within a few growing seasons. Eradication requires multiple broadcast applications of herbicide and follow-up spot treatments over a period of 4 to 10 years. Establishment of pine trees or other crops should not be attempted for at least 4 years after control measures are initiated.
In order to develop an effective kudzu control program the site should be carefully inspected. Factors such as age and vigor of the kudzu, terrain, and the presence of sensitive crops, high value trees, and streams should be considered in selecting herbicides and method of application. Herbicide guidelines for several common situations are described below. They are also summarized in the herbicide use table at the end of this document.
Open Kudzu Patch
The open kudzu patch containing no obstructions or sensitive areas represents the ideal treatment situation. Herbicide selection is primarily based on effectiveness and cost. Tordon 101® Mixture at a rate of 1 gallon per acre or Tordon K® at ½ gallon per acre gives the best control per dollar invested. In kudzu patches older than 9 years or deeper than 5 feet, 2 gallons of Tordon 101 should be used. The most effective application is with a tractor mounted spray rig delivering 40 gallons of solution (water and herbicide) per acre in patches 1 to 6 feet deep and up to 100 gallons of solution in patches greater than 6 feet deep. To insure complete coverage, a crosshatch pattern of application is recommended. Apply half of the recommended rate of herbicide in one direction and then apply the other half in right angle passes. The above products are most effective when applied from May to September.
Burning the kudzu patch in the spring prior to treatment is often recommended. Prescribed fire will provide control of small, recently established kudzu plants, sever plants to ground line in tree draped areas, and make visible hidden gullies or obstructions. Herbicide application should be conducted after regrowth is 2 to 3 feet deep.
After the broadcast treatment the first year, it is recommended that nothing be done the second year if complete coverage and "brown-up" was achieved with the first application. A broadcast treatment in June of the third year (1 gallon of Tordon 101 per acre) will then control most, if not all, resprouting. Inspection of the patch at the end of the third year and the beginning of the fourth year along with spot application with a back-pack sprayer when required (1 pint of Tordon 101 Mixture in 2½ to 5 gallons of water) will give complete control under most circumstances. However, sites should be monitored for several years to assure that eradication is complete.
Tordon 101 Mixture will kill pines and hardwoods if they are sprayed, but up to 1 gallon per acre can be applied under pines older than 15 years. It should not be applied in a young plantation or to older plantations that are stressed from drought or overstocking. Furthermore, pines should not be planted for 6 to 9 months after the last application. Tordon products should not be applied near streams or gullies where the herbicide may leach into running water sources. Also_observe the label regarding use on soils where leaching into the water table is a high risk.
Tordon 101 Mixture and Tordon K are "restricted use pesticides" requiring certification by the user. Certification is obtained by passing an exam offered through the Cooperative Extension Service. Various fees are charged depending on the status of the user. Landowners can apply for permits, without charge, at their county extension office.
Near Streams and Other Water Sources
As mentioned previously, Tordon products should not be used near streams. An alternative compound, Veteran 720® at a rate of 2 to 3 gallons per acre can provide good control in this situation, but it should not be used directly over water or near water that will be used for irrigation or domestic use. Labeled rates of glyphosate formulated in the products Accord® and Rodeo® can also be used near water. However, these products are not likely to give complete kill of well-established kudzu. A handgun nozzle on a tractor sprayer can be used to apply these products into deep draws or along branch heads. Several successive broadcast applications plus spot applications will likely be required to achieve complete control.
Kudzu vines growing up large trees should be severed before treatment. If pines are greater than 15 years old or greater than 8 inches d.b.h., treatment of kudzu with 1 gallon per acre of Tordon 101 Mixture is suggested. However, the landowner should proceed cautiously. Tordon 101 will likely cause temporary damage to pines. Damage may be greater in trees already stressed by drought, disease, etc. Also, this treatment is not recommended during years of high pine bark beetle infestations since trees stressed by the herbicide will likely attract beetles.
Young Pine Plantations
In young pine plantations older than two years, Oust at 8 ounces of active ingredient per acre can be broadcast over the seedlings. As above, several treatments will be necessary for effective control. For treating over 3 to 4 year-old loblolly pines, apply Escort® at 3 to 4 ounces per acre. Another product that can be used over pines and many hardwood species is Transline®. Apply Transline at 21 fluid ounces per acre. This herbicide will injure legumes including redbud, honey locust and black locust. Use a nonionic surfactant at 1 qt per 100 gal of spray with each of the above herbicides.
Sensitive Crop Areas
As with any herbicide application, care should be taken to apply herbicides only to areas meant for treatment. This is best accomplished by careful application. To avoid drift, broadcast application of solutions should not be done when wind speed exceeds 5 mph. Fifty to 100 foot buffers between broadcast application and sensitive crop areas can help ensure that problems of chemical trespass are minimized. In the buffer area treat kudzu with Accord at 4 quarts per acre or a 2% directed foliar spray.
Spike 80 DF® is recommended for severe infestations on non-croplands and appears particularly suited for kudzu control in fence rows. An initial fence-row treatment should provide good control for more than two years. Spike 80 DF is not recommended (or labeled) for treatment before pine establishment. Furthermore, roots extending into treated areas can result in the death of trees at distances up to twice the height of the tree.
Effective herbicide treatments have been developed for many kudzu control situations (refer to the herbicide use table). The key words in kudzu eradication are persistence and complete kill. By following the suggestions in this guide a landowner will, under most circumstances, be able to return land taken over by kudzu to productive use.
Herbicide Use Table. Remember that all herbicides must be used according to their label directions. If you are not sure, do not apply.
|Herbicide||Application Dates||1st Year Rates||2nd Year Rates||Retreatment Type||Approx.b Unit Cost of Herbicide||Total Cost of Herbicide Year 1 & 2|
|Product per acre||($/Unit)||($/Acre)|
Dow Tordon 101 Mixturea
Dow Tordon Ka
spot & broadcast
spot & broadcast
|August-October||3 gallons||3 gallons||broadcast||27/gallon||162|
broadcast or spot
broadcast or spot
Elanco Spike 80DF
|All Year||5 pounds||5 pounds||spot & broadcast||24/pound||120|
a. Restricted-use herbicide that requires a permit to purchase. Landowners can apply for permits at their county agent’s office.
b. Costs vary depending on the amount purchased, rebates, etc. These 1990 prices should be used for relative comparisons and should not be thought of as absolute values.
Note: The use of brand names or registered trademarks as presented in this article does not imply endorsement of these products by the Clemson Cooperative Extension Service nor is any discrimination intended by the exclusion of products or manufacturers not named.