June 02, 2023
When threats to white-tailed deer are discussed, topics usually turn to predators and diseases; however, there often are less obvious threats that on the surface may seem innocuous.
Because whitetails are K-adapted species, meaning their population processes are mostly governed by habitat, the impact of invasive species of plants can be significant and insidious. In this series, I will be presenting what I consider to be the top five culprits that have managed to take a foothold on the American landscape.
The story begins during the Victorian Age (1837-1901), as England became the major political, economic and military power on Earth. The British Empire reached far and wide across the globe, and international trade brought interest in all things foreign. Increasing wealth brought interest in gardening in a much different way than growing vegetables for the table; the Victorian Garden became the rage.
This gave rise to a new breed of explorer, men and women called “plant hunters.” The grandfather of them all was Francis Masson, a Scottish botanist and gardener, who sailed with James Cook on HMS Resolution to South Africa. It is reported he rounded up over 500 species of plants and sent them back to England’s growing gardens. His success was followed by Ernest Wilson, George Forrest and Harold Comber, who enjoyed “rockstar” reputations among English gardeners.
At the Centennial International Exposition in 1876 held in Philadelphia, exotic plants were quite the hit; especially those from the Orient. Among these plants were what would become some of our greatest enemies of quality deer habitat, not to mention impacts on agriculture. Most of my “dirty 5” invasive plants first made their appearance at the Exposition.
The western world learned about Kudzu (Pueraria montana) at the Exposition. There are about 15 known species of these plants, principally from China, Japan, Taiwan and India. Literally for centuries, the roots of these plants served as both food and medicine. The roots have been ground into flour for at least 2,000 years, while the stems are used for fiber and clothing.
The Kudzu variety that made its way to the Exposition was brought from Japan. Even in those days, the U.S. government frowned on bringing foreign plants into the country, so the ones exhibited at the Exposition were destroyed according to law.
Kudzu made its return appearance at the New Orleans Exposition in 1883, after which it remained in the U.S. A fellow named C.E. Pleas found that Kudzu could serve as a livestock forage, mostly due to its remarkable ability to grow quickly. How quickly? There is an often-repeated story about a family that went on vacation for two weeks, and when they returned the Kudzu vine next to their house had completely covered the structure.
Pleas began selling Kudzu by mail order around 1900, mainly in the form of root cuttings. Then the U.S. Government got involved. Government conservation programs often have had a very negative outcome; certainly, this is the case with Kudzu. In the 1930s, the Soil Erosion Service, later called the Soil Conservation Service and now the National Resource Conservation Service, initiated a program to encourage planting Kudzu for erosion control.
It was during the first 30 years of the 20th Century that farming practices created tremendous soil erosion issues, and the agency wanted to find ways to reduce erosion. Kudzu, due to its fast growth, seemed like a logical solution. They supplied plants and even paid $8 an acre to farmers for planting Kudzu; and, by 1950, millions of acres had been introduced to Kudzu.
By 2000, Kudzu had moved from a cure to a problem to an even bigger problem. It became known as the “plant that ate the South!” Today Kudzu is one of our greatest invasives! It is reported Kudzu control costs some $50 million a year.
Yet, if it was promoted initially as a livestock forage, is it not possible Kudzu could be a benefit to deer? Yes, deer eat the leaves of the plants, but if cattle cannot keep it under control, why would deer be able to do so? A cow eats about 24 pounds a day, while a deer eats 4-8 pounds. Deer do indeed eat Kudzu, and some deer managers have planted it as food and cover for whitetails; however, it is impossible for deer to control growth. The vines tend to choke out other vegetation, even trees, and they lose their leaves during the winter. I have been in areas of Mississippi where the only “forest” you see is an undulating landscape of Kudzu vines that hide dying trees.
To control Kudzu requires a long and expensive eradication program requiring a multifaceted approach. On the surface, you would think that prescribed fire would control it. In reality, Kudzu loves fire, as it comes back quickly from the roots that may be as big as a human; and fire increases areas for vine growth. Over-grazing it with goats helps on small, fenced areas, but is totally illogical for forest landscapes. Grubbing the roots out is only marginally effective, since any part of a root left in the ground will sprout. So, that leaves us with the heavy-duty herbicides such as Triclopyr, 2,4-D and Dicamda. Yet, even with these effective chemicals ultimate eradication will take years to succeed. Here is how I have managed to control it in some areas.
If the Kudzu has reached the point where it has climbed into the canopy of the forest, you have a real problem on your hands! Aerial spraying is not practical, as these chemicals are non-selective and will also kill beneficial trees and shrubs.
One solution is to use a bulldozer to make paths through the forest of vines, then drive down each path and use a side spray boom to wet the bottom part of the vine matt. If you are lucky enough to just have vines that are low, you can use a backpack spray unit or side sprayer to treat them. This probably will take more than one year to accomplish.
What about biological control? A total of 116 phytophagous insect species in 31 families and 5 orders are known to attack Kudzu. The bad news is studies have shown these account for less than 20 percent defoliation. As far as disease goes, there is a false rust (Synclzytriun nlinutum) that has some promise. However, Kudzu is known to spread viruses that affect soybeans! The bottom-line? The best control mechanism for Kudzu is to not let it become established on your land. Using herbicides on invading runners and shoots can be quite effective, as long as you reapply every time Kudzu emerges.