Pueraria montana

Kudzu

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Introduction

An estimated 2 million acres of forest land in the southern United States is covered with kudzu. Kudzu was promoted as a forage crop and an ornamental plant when it was introduced to the U.S. at the Philadelphia Centennial Exposition in 1876. Many southern farmers were encouraged to plant kudzu for erosion control from the mid 1930’s to the mid 1950’s. In 1953, kudzu was removed from the US Department of Agriculture’s list of permissible cover plants due to its recognition as a pest species. Currently in Florida, kudzu has been documented in 14 counties and is listed as a Category I invasive species.

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Description

Kudzu is a climbing, semi-woody, perennial vine in the legume family that has the potential to reach up to 100 feet in length. Stems can reach the diameter of ½ to 4 inches, but there are report of old ‘stumps’ nearly 12 inches across in Georgia.  Alternately arranged leaves are compound with three broad leaflets up to 4 inches across. Leaflets may be entire or deeply 2-3 lobed with hairy margins. Flowers are ½ inch long, purple, highly fragrant and borne in long hanging clusters. Flowering occurs in late summer, followed by the production of brown, hairy, flattened, seed pods that contain three to ten seeds.

The spread of kudzu in the U.S. is thought to be primarily runners, rhizomes, and vines that root at the nodes. Kudzu may also spread via seeds. There are only one to two viable seeds produced per pod, and seeds are contained within a hard seed coat generally requiring scarification for germination. Kudzu has a massive tap root: 7 inches or more in diameter, 6 feet or more in length, weighing as much as 400 pounds! There can be as many as thirty vines growing from a single root crown.

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Impacts

Kudzu will grow over anything in its path (other plants, buildings, road signs) and eventually kill other plants it covers because it blocks out sunlight. Kudzu will also girdle stems and tree trunks, break branches, and uproot trees and shrubs through the masses of vegetation produced.  Kudzu has been reported to grow roughly one foot per day once established.

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Management

Preventative:

Total eradication of kudzu is necessary to prevent re-growth. This requires continuous monitoring and thoroughness when treating. To prevent reestablishment, replanting after treatment is critical. Prevent the production of viable seed and destroy the plant's ability to reproduce vegetatively.

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Cultural:

Young colonies can be eradicated in three to four years if plants are overgrazed or persistently cut back repeatedly during the hottest temperatures of summer. Close grazing for three to four years can totally eliminate kudzu when at least 80% of the vegetative growth is continuously removed by livestock.  An old rule of thumb is 8 goats per acre stocking rate for kudzu control.

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Mechanical:

The massive root system and crowns must be destroyed for long term control of kudzu. Cut vines just above ground level and destroy all cut material. Close mowing every month for two growing seasons or repeated cultivation may be effective. Pre-burning, cutting, hand digging and disking will weaken the roots and aid in control when used in conjunction with herbicides.

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Biological:

Biological control agents are being investigated, but the recent introduction of asian soybean rust is thought to be very devastating to kudzu.

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Chemical:  

Glyphosate, dicamba (Clarity), chlopyralid (Transline) and triclopyr (Remedy) can be used to control kudzu.  Follow label directions and precautions.

Open Patches on Level Ground
2,4-D liquid applied as a foliar spray. Treatment should be done when all stems are actively growing. 2,4-D is recommended at a rate of one gallon per acre for younger kudzu infestations and two gallons per acre for patches older than ten years.

Near Streams, Ponds, Wetlands, or Ditches
Dicamba and triclopyr are recommended for sites near water, although should not be sprayed directly onto water. Both herbicides are dicot-specific herbicide used as a foliar spray. Application rate is two gallons per acre for dicamba and 2 quarts per acre for triclopyr.  August or September are recommended months for application, but moderate rainfall is required for good growth.

Residential and Environmentally Sensitive Areas
Glyphosate is the safest herbicide for use in residential and environmentally sensitive areas. Glyphosate is a non-selective, foliar-applied herbicide, with some formulations licensed for use over water.

Clopyralid is readily absorbed by foliage and roots and is translocated throughout the plant. This herbicide is targeted to three plant families: legumes, smartweeds and composites. At 21 ounces per acre, clopyralid has the benefit that it may be used near trees, grasses and dicots, other than the three target families, without damaging them. Clopyralid has not proven effective in eradicating older infestations of kudzu, but may be helpful in treating young patches and in controlling the spread of older plants.

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Helpful Notes:

Surfactant – 0.25% is the standard rate for all foliar herbicide applications, 2 teaspoons per gallon.

Dry time – generally 4-6 hours is adequate, but the longer the better for glyphosate

Pay particular attention to herbicide labels near wetlands or bodies of water.

The use of trade names in these publications is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label.

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References and Useful Links:

Floridata Homepage

University of Florida Center for Aquatic and Invasive Plants

University of Florida’s Cooperative Extension Electronic Data Information Source

Langeland, K.A. and K. Craddock Burks. 1998. Identification and Biology of Non-Native Plants in Florida's Natural Areas. IFAS Publication SP 257. University of Florida, Gainesville. 165 pp.

The Plant Conservation Alliance's Alien Plant Working Group. Weeds Gone Wild: Alien Plant Invaders of Natural Areas

Pacific Island Ecosystems at Risk (PIER). Plant Threats to Pacific Ecosystems

Invasive Plants of the Eastern United States

USDA Natural Resources Conservation Service. Plants Database

Kansas Department of Agriculture, Plant Protection and Weed Control Program

Missouri Department of Conservation: Vegetation Management Guidelines for Kudzu

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