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Arbor Culture 6/29/14: Plant pest: Skunk vine

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Exotic plants brought here with good intentions can end up causing problems

Note from Eric: Invasive plants are a problem throughout Florida. These are plants which were introduced from elsewhere, generally outside the United States, often with good intentions. Many of these plants have adapted well to Florida’s climate and, without natural pests or diseases to keep them in check, have “invaded” and in many cases overrun our natural ecosystems.

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Several species are particularly prevalent in our area. It is my intention to introduce readers to these invasive plants to make them aware of their existence and educate them on preventing further spread and assisting in their control. To this end, I am using a guest writer, Alicia Campanella, who has contributed articles to the newsletter Florida Land Steward. Because her articles are informative and well-written, I will be using them, with her permission, from time to time. Her articles are titled “Plants Behaving Badly.”

In the late 1880s, an especially interesting but rather unpleasant exotic plant was introduced to Florida. It goes by the name skunk vine, or Paederia foetida. Foetida literally translates to “bad smelling” in Latin. And all it takes is crushing the leaves, or any part of the vine, to see why this sulfur-rich plant is known for being so malodorous!

Skunk vine is native to eastern and southeastern Asia, but was introduced to Florida with the intention that it would be a potential fiber crop. Like most exotic species introduced for commercial purposes, within a matter of years the consequences of the introduction became clear. Skunk vine quickly escaped and began invading Florida’s wildlands. It was classified by the Florida Exotic Pest Plant Council as a Category 1 exotic/invasive as early as 1993, and is currently found in 17 counties in Florida. 

In addition to its awful smell, skunk vine can also be identified by its leaves, which are narrow and heart shaped, with sharply pointed tips. Its flowers are often pink, light purple or gray, all with a red center. The fruits are brown, typically found with two seeds that are black in color. It is a woody, thornless vine that often uses other vines to make its way high into the canopy.

Its invasive nature can be credited to the fact that it reproduces not only via seeds, but also vegetatively. It roots at its nodes, and will grow along the ground until it finds a suitable host (sometimes another vine) to begin its upward climb. Within a matter of time, it shades out and kills its host tree, as well as plants in the mid-canopy and understory, similar to the effects of air potato and kudzu. Unfortunately, like most successful invaders, skunk vine thrives in a variety of ecosystems, from wet lowlands to dry upland habitats. 

Skunk vine is currently considered a threat to all habitat types in Florida, including economically important ones such as citrus groves. Two federally listed endangered plants are also threatened by skunk vine: The Brooksville bell flower (Campanula robinsiae) and Cooley’s water willow (Justicia cooleyi). Young pines and other species vital to the survival of many other species are also at risk.

Many eradication methods have been experimented with. They include fire, flooding and manual removal. To date, the most effective method is the use of herbicides containing glyphosate (Roundup or equivalent) and triclopyr (Garlon). The latter is only available to licensed applicators.

Applications are most effective during the vine’s active growing seasons — spring and summer. As always, carefully follow manufacturers’ safety labels and use personal protective equipment. Biological control methods are currently being researched.

In Asia, species of sawflies and leaf beatles have been identified as suitable hosts, and these insects adequately control native populations of skunk vine. Many years of testing would have to be undertaken in Florida to ensure that only the target species would be adversely affected by insects introduced for this purpose. Also, maintaining a diverse population of different plant species is a great way to deter monocultures of any exotic species.

For more information about this plant, other invasive exotic species, funding, and regional efforts to prevent and control infestations, see the Florida Invasive Species Partnership website at www.floridainvasives.org.

 

Alicia Campanella has studied environmental science and participated in a monthlong reforestation project in the Amazon, after which she volunteered with the Florida Park Service. She became a park ranger and worked at Fakahatchee Strand for a few years, specializing in exotic species management. She is now finishing her degree in environmental science.

Eric H. Hoyer is a certified arborist, a certified forester, a registered consulting arborist and a qualified tree risk assessor with Natural Resource Planning Services Inc. He can be contacted at erich@nrpsforesters.com.