Issue 12, July 17, 2009
Controlling Kudzu (or at least slowing it down a little)
Legumes can be easily spotted across the state of Illinois this time of year. Typically, soybean is the legume that comes to mind but we have another that you should be on the look out for. Kudzu (Pueraria lobata or P. montana) is a perennial, trifoliate vine that is native to Asia. It was promoted widely in the 1930's for erosion control, fodder for livestock, and shade. Unfortunately, other plants are often shaded and killed by this plant, as were the livestock that fed upon it. OK, so the latter may or may not be true. I am merely speculating here. Though I think it is a slight understatement to simply call this plant "aggressive." A source I read calls it "rampantly-growing" and "high climbing." One shouldn't take too lightly a plant that is capable of girdling trees or breaking tree branches from its sheer weight alone. Another problem it poses is that it serves as a host for soybean rust.
Kudzu is not even listed in my 1981 edition of Weeds of the North Central States. This "vine that ate the south" used to be thought of as a problem in the southern U.S. only. Then in the 1990's, southern Illinoisans really began to take notice of this weed. A few years ago, kudzu made it as far north in Illinois as Evanston. There have been kudzu populations (105 reported in 2001) across the state including the one in Peoria that made the news a few years back. This past winter I was telling a class about Kudzu and a man sitting in the front told me that he had this plant growing at his house near Kenny, Illinois. He appeared quite alarmed upon learning the plant's identity. Of course, his next question was that of control. Kudzu is a Noxious weed in Illinois and its control is required by law. Just to be on the safe side, law makers also included it in the state's Exotic Weed Act to help prevent the spread of this plant by man. It is illegal to plant or sell Kudzu in Illinois. I'm not sure who would sell this plant or who would buy this plant, but I digress. There are various reported uses for the plant. Over the years I've been told of baskets woven of the vines, flour ground from the roots, quiches made with the leaves, and remedies made for alcoholism. One such ad claims you can "end your embarrassment from excessive drinking" with kudzu. Perhaps this is accomplished by hiding behind the vines, but I have seen kudzu pills for sale. Unfortunately, these diverse uses don't seem to be able to keep the kudzu population in check.
Kudzu can spread by seed, fragmentation of vines, and root expansion. The vine is quite aggressive in its growth and it is capable of growing up to a foot a day! In the south, the vines cover roads, crops, trees, utility poles, etc. Kudzu prefers open, sunny sites with well drained soils but it can tolerate a variety of growing conditions including severe winters which was once thought to keep kudzu from being a problem in this state. It can be found growing along roadsides, forest edges, and other undisturbed sites.
The leaves are comprised of 3 large, usually lobed, oval leaflets, with the center one on a longer stalk. Leaves are alternate on the stem and hairy when young. The flowers are reddish purple generally but can be white or pink. They are borne on spikes that emerge from the leaf axils. They are sweet smelling (almost grape scented) and appear August through September. Dark brown, hairy, flat, 2-3 inch seed pods are then produced. Vines become woody with age and older vines can be roughly 3 inches in diameter. The roots are tuberous and fleshy and can reach 12 feet deep.
For the last decade, the Department of Natural Resources, Illinois Department of Transportation, Natural Resource Conservation Service, U.S. Forest Service and the U.S. Fish and Wildlife Service have worked in cooperation to control known populations of Kudzu. Their kudzu fighting forces grew recently upon the creation of the River to River Cooperative Weed Management Area (CWMA). This is a partnership among 12 federal and state agencies, organizations, and universities including the University of Illinois that is aimed at coordinating efforts and programs for addressing the threat of invasive plants. To learn more about their fight against kudzu, go to http://www.rtrcwma.org/kudzu/.
What about kudzu battles in the home garden? Cutting and mowing (close to the ground) may be used to slow the spread by weakening the plant, but be sure to clean mowers afterwards to prevent further spread into other areas. Goats, pigs, and sheep can be used for grazing in certain situations. Herbicides tend to be the conventional method of control for kudzu. Home gardeners can use brush killers that contain triclopyr. Also effective are 2,4-D and dicamba. Glyphosate can be used but reports have shown it to be less effective than the previously mentioned herbicides. These are available at most garden centers.
Depending on where the kudzu is growing, it is possible that clopyralid (Stinger and Transline for example) may be used. This is actually the herbicide of choice by many for kudzu but it can't be used by just anyone just anywhere. Stinger is generally thought of as being the ag product, Lontrel is for turf and ornamentals, and Transline is used in rights-of-way situations, although, the labels list additional specific areas. Please note that Lontrel may not be used on residential lawns. Interestingly enough, kudzu is specifically mentioned on the Transline and Lontrel labels only.
- Stinger label: http://www.cdms.net/LDat/ld02P012.pdf.
- Lontrel label: http://www.greenbook.net/Docs/Label/L47578.pdf.
- Transline label: http://www.cdms.net/LDat/ld0BB014.pdf.
Your local agrichemical retailer may be able to order these products for you. Be sure however, that your application site is listed on the label and that the product is not for application by professional applicators only - unless of course you are one.
Carefully read and follow all label directions. Applications may be made to the leaves, stems, or cut stems. Refer to the label for guidance. Bear in mind that complete eradication of kudzu is the goal and repeat applications will likely be needed as this is a difficult weed to control. Depending on the severity of the infestation, and the number of seeds in the soil, it could take several years to achieve eradication. The herbicides listed here are capable of damaging nearby sensitive plants. Glyphosate is non-selective and will kill or severely injure all plants that it comes into contact with. Applications need to be targeted and the wind speed should be between 3 and 10 mph to avoid herbicide drift to off-target plants.
Lastly, please report any kudzu populations to Jody Shimp with IDNR. He can be reached at 618-435-8138 ext. 127 or firstname.lastname@example.org. For assistance with weed identification, please contact your local University of Illinois Extension office.--Michelle Wiesbrook