‘Beach kudzu’ threatens South Carolina dunes

By Tom Lollis

Clemson scientist Jack Whetstone with beach vitexVitex rotundifolia, a sprawling woody shrub native to beaches in Hawaii and Korea, once showed promise as a stabilizer for South Carolina’s fragile beach dunes. It was drought resistant, tolerant of salt and blowing sand, and fast growing.
   
It may be too tough, according to Jack Whetstone, Clemson Extension’s aquaculture specialist and expert in aquatic nuisance species. Vitex, often called “beach kudzu,” quickly crowds out native dune plants such as sea oats, beach amaranth and sweetgrass. The roots can also entangle sea-turtles and destroy their nests.
   
“Betsy Brabson, a Georgetown County resident and sea turtle volunteer, was one of the first to spread the word about possible problems with vitex,” said Whetstone. She noticed it at DeBordieu Beach, one of the places she monitors for turtles.
   
Pawley’s Island, the Isle of Palms, Folly Beach and Seabrook Island are some of the places vitex has been found.
   
“The plant is not illegal in South Carolina, but it could become so,” said Whetstone, who is part of a team of Clemson scientists studying vitex at the Belle W. Baruch Institute of Coastal Ecology and Forest Science. The institute is located at Hobcaw Barony near Georgetown and focuses on environmental issues affecting the lower coastal plain.
   
Chuck Gresham, a Clemson forest resources scientist, inventoried dune species at nine sites with help from a summer intern, Amber Neal. He has concluded that vitex simply crowds out other species. Deep shade keeps sprouts of any other plants from developing.
   
Will Conner and Lin Roth, also forest resources scientists, have looked at germination and how vitex seeds spread. Roth is investigating whether birds play a role in the process.
   
Whetstone has treated several plants around DeBordieu with a range of herbicides to see which is most effective in killing vitex. Early observations of the tests look promising.
   
Vitex is just one of many nuisance plants found in Georgetown County. Others include phragmites (common reed), kudzu, Chinese tallowtree, water hyacinth, alligator weed and privette.
   
Clemson University, through Extension and the Department of Plant Industry, works in partnership with other agencies – such as the S.C. Department of Natural Resources and DHEC’s Office of Ocean and Coastal Resource Management – to protect the environment all over South Carolina from invasive species, whether aquatic or dryland plant or insect.
   
The state’s noxious weed list includes 26 aquatic species. Dryland plants such as Tropical Soda Apple, witchweed and cogongrass are also on the public enemy list. Insects such as gypsy moth, imported fire ant and boll weevil are also invasive species. The weevil is proof that control measures can work. Once a plague for cotton growers, the weevil is now rarely found in the state thanks to an eradication program led by Clemson plant industry professionals.