Kudzu can grow a foot per day, and today it covers nearly seven million acres in the South.
Now listed as a federal noxious weed, kudzu was imported to prevent soil erosion and to feed livestock. The semi-woody plant covers large tracts of land from eastern Texas to the East Coast and as far north as Maryland. Kudzu climbs, covers and eventually kills trees, destroying the timber-producing value of these lands. It reduces land productivity by millions of dollars yearly.
A recent Mississippi State University study evaluated the after-tax financial returns of controlling kudzu with herbicides and then planting pine or oak plantations on lands formerly covered by the vine.
"As the population grows and land use changes over time, the need to reclaim unproductive areas where kudzu has taken over is essential for timber production," said Donald Grebner, forestry professor and economist in the university’s Forest and Wildlife Research Center. "Reclaimed land could also be used for wildlife habitat and recreation, improving the financial stability of local economies."
To determine financial returns of reclaiming kudzu-covered land, scientists first needed to determine the best way to kill the creeping invader.
MSU Forestry Department head Andrew Ezell has tested different herbicide treatments on kudzu patches in the state for more than 20 years. He, along with colleagues in South Carolina, treated patches of the weed and then observed growth estimates four times after initial application.
For this study, scientists compared seven different strategies for eradicating kudzu patches and then establishing either pine or hardwood plantations. Management scenarios included using different herbicide applications, different types of chemical dispersal methods and different tree species after eliminating the vine.
"Controlling kudzu is difficult and expensive," Ezell said. "Many of the herbicides that can be used to control kudzu affect the soil such that trees can’t be planted immediately after application."
The study found a broadcast application of Escort XP—a selective herbicide manufactured by DuPont—to be the most cost-effective way to control kudzu patches. Escort XP is appropriate for both young and old kudzu patches, and it works for reforesting the area with pine or oak.
Forest economists used the land expectation value on an after-tax basis to evaluate the feasibility of the control regimes. Land expectation value is the present value of all future costs and revenues of an asset, including forestland.
"For example, treating kudzu aerially with Escort XP and then replanting in pine would yield an estimated $1,460 per acre in revenue after taxes," Grebner said.
An aerial application of herbicide followed by replanting in oak would yield an estimated $317 per acre.
"The biggest difference in the two is the maturity time, with pine having multiple cuttings in a shorter period of time and oak only having one cut at 30 years and then final harvest at 50 years," Grebner said. "However, by removing kudzu and planting in either oak or pine, the land expectation value increases."
Ezell said controlling kudzu with herbicides can be a costly venture, especially for private landowners.
"Fortunately, there are multiple federally funded cost-share programs that offer assistance to private landowners to combat the spread of nonnative invasive plants such as kudzu," Ezell said. "Incentive programs offered through the government have paid up to $87 per acre to eradicate the invasive plant."
These programs can make a world of difference to landowners. Recovering any portion of initial cost to control kudzu will reduce costs and increase returns, leading to higher land expectation values.
"Clearly, landowners can reap both environmental and ecological benefits by turning unproductive, kudzu-covered land into forest," Ezell said.