Good News for Eradicating Cogongrass in the South

Research shows success using combinations of treatments and timing

by Zoё Hoyle, SRS Science Delivery Group
Cogongrass invading forested areas. Photo by Charles T. Bryson, courtesy of Bugwood.org.

Cogongrass invading forested area. Photo by Charles T. Bryson, courtesy of Bugwood.org.

Over the past decade, U.S. Forest Service researchers have been working with university cooperators to find some way to slow down or stop the relentless spread of cogongrass. This last fall, Auburn University researchers reported results that demonstrate, for the first time, that patches of cogongrass can be eliminated completely within three years — showing that eradication of the invasive plant is actually possible for many land managers.

Cogongrass is in a class of its own. Ranked the seventh worst weed in the world, it grows on every continent except Antarctica and is particularly destructive to the ecological structure of forests and natural areas, where the weed can literally take over understories.

Cogongrass currently occupies an estimated 66,000 forested acres in the U.S. South. It’s classified as a noxious weed in Alabama, Florida, Georgia, Mississippi, South Carolina, Texas, and Virginia, where it is widely believed to be impossible to eradicate. Estimated to spread 800 acres a year, cogongrass could infest 100,000 forested acres by 2060.

“Cogongrass grows mainly by extending rhizomes, which are like creeping rootstalks,” says Jim Miller, emeritus Forest Service Southern Research Station (SRS) researcher who helped with the study. “Cogongrass rhizomes are exceptionally aggressive, strong, and resistant to heat and water stress, making the plant a formidable and frustrating opponent.”

For the recently published study, researchers established a field study in two locations in southwestern Alabama where they applied herbicide treatments —  glyphosate, imazapyr, and a mixture of both —  in May, August, or October for three consecutive years.

“I consulted on experimental design, but Erwin Chambliss, senior technician with the SRS Restoring Longleaf Pine Ecosystems unit, did the heavy lifting for SRS, digging and separating rhizome samples in the field during the hot Alabama summer,” notes Miller.

The study found that although responses of cogongrass to the treatments varied by location, 36 months after the initial treatment cogongrass shoot and rhizomes were completely eliminated and 100 percent visual control achieved at both locations using several combinations of herbicide treatments and timing.

“The findings provide a ray of hope for actually eradicating cogongrass,” says Miller. “Land managers now have a clear option in fighting this noxious weed.”

In related news, the Georgia Forestry Commission’s Cogongrass Taskforce recently announced that for the first time since the Forest Service Southern Region’s Forest Health Program began funding cogongrass control in Georgia in 2004, there are more dead cogongrass spots in the state than new areas of cogongrass being reported.

The taskforce encourages citizens to report cogongrass occurrences and treats every infestation reported in the state, respraying as needed until the spots are negative for cogongrass for three years and receive “eradicated” status.

This effort confirms the hope that a weed that’s consumed millions of dollars in control efforts – and millions more in the economic and ecological consequences of cogongrass infestations – can indeed be eradicated in Georgia.

For more information, email Jim Miller at jamesmiller@fs.fed.us

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Posted in Forest Health Protection, Invasive Plants, Longleaf Pines, Restoration, Threats

Flowers on the Forest Floor: Herbaceous Contributions to Ecosystem Processes

by Sarah Farmer, SRS Science Delivery
Black cohosh, a native understory plant, is often found in rich cove forests. Photo by David Stephens, courtesy of Bugwood.org.

Black cohosh, a native understory plant, is often found in rich cove forests. Photo by David Stephens, courtesy of Bugwood.org.

Plant diversity in eastern U.S. forests comes not only from trees, but from the ferns, wildflowers, and other herbaceous plants on the forest floor.  Some researchers have found that as much as 90 percent of plant diversity is due to these understory species. “Until recently, not much was known about the role these plants play in ecosystem processes,” says U.S. Forest Service scientist Katherine Elliott.

In 1998, Elliott and her colleagues began studying the understory in a forest at the Southern Research Station Coweeta Hydrologic Laboratory in western North Carolina. They designed the 14-year study, recently published in the journal Ecosystems,  to see whether herbaceous plants contributed to carbon and nutrient cycling and whether they limited the amount of light and nutrients reaching tree seedlings. “We also wanted to determine whether the quick turnover of biomass  — as the aboveground portions of herbaceous plants die and decompose quickly – helps trees to grow,” says Elliott.

Elliott and her colleagues installed 18 plots in a rich cove forest that was dominated by tulip poplar, American basswood, buckeye, birch, black cherry, and white ash. Rich cove forests tend to have relatively high water availability and rich, deep soils, and often harbor lush understories of native herbaceous plants such as ginseng, black cohosh, trilliums, ferns, Jack-in-the-pulpit, and many other species.

To find out whether these herbaceous plants contributed to carbon and nutrient cycling, Elliott and her colleagues separated the study area into treatment plots and untreated controls.  In some plots, herbaceous biomass was added, and in other plots it was removed. Researchers measured mature tree growth, litterfall, and tree seedling recruitment numerous times over the course of the study, and also measured soil processes such as plant available nitrogen (the amount of nitrogen that is converted into forms plants can use for growth), and the amount of carbon dioxide released by plant roots and soil organisms.

The scientists found that plots with added herbaceous biomass had twice as much available nitrogen as control plots. “Our study showed that inputs of herbaceous plant material increases nitrogen in foliage of mature trees and contributes to soil available nitrogen,” says Elliott. Mature trees in these plots also produced more leaves, and despite the doubling of herbaceous plant material, the forest floor was unchanged, suggesting that the added herbaceous plant material decomposed very quickly.

In plots where the herbaceous biomass was removed, tree seedlings were far more likely to survive, suggesting that the herbaceous plants out-compete tree seedlings, most likely by limiting light. Even the red maples, which can tolerate more shade than other tree seedlings, had greater survival in plots where the herbaceous plant community was removed. “Our study shows that herbaceous plants affect tree seedling survival,” says Elliott. “However, they are an important part of the nitrogen cycle, and although rarely studied, play an important role in forest ecosystems.”

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For more information, email Katherine Elliott at kelliott@fs.fed.us.

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Posted in Experimental Forests, Forest Watersheds, Restoration, Upland Hardwoods

Michael Ulyshen Receives U.S. Forest Service Early Career Scientist Award

by Patty Matteson, SRS Partnerships and Strategic Initiatives
Michael Ulyshen. Photo by Sean Cook.

Michael Ulyshen. Photo by Sean Cook.

Michael Ulyshen is being recognized with the U.S. Forest Service Early Career Scientist Award, but his achievements in his short time with the Forest Service are remarkable. Ulyshen is a research entomologist with the Southern Research Station (SRS) Insects, Diseases, and Invasive Plants unit. During the last five years, he’s been first author on 34 peer-reviewed publications along with three book chapters, five invited presentations, and received international recognition.

Ulyshen’s first assignment with SRS was in Starkville, Mississipi, with the Termite team. While the termite team’s focus is testing all candidate termiticides (pesticides specifically used to kill termites), Ulyshen’s research took a different path.  “I was looking at the roles termites play in the forest, specifically their contributions to wood decomposition and effects on nutrient cycling,” Ulyshen said.

His exemplary research was recently recognized by the Royal Entomological Society. In September, Ulyshen will deliver an invited lecture sponsored by the Royal Entomological Society at the Ento ’15 Annual National Science Meeting and International Symposium at Trinity College in Dublin, Ireland.

Ulyshen’s international research previously took him to New Zealand, where he received the 2011 International Mobility Fund from the Royal Society of New Zealand, an independent government body in New Zealand that provides funding and policy advice in the sciences and humanities. In New Zealand, Ulyshen spent 10 weeks working with a colleague in Monterey pine (Pinus radiata) plantations on a study aimed at quantifying native biodiversity using remote sensing technology.

“Michael’s exceptional productivity and this early international recognition of his work are indicative of his tremendous career potential,” said Bud Mayfield, project leader of the SRS Insects, Diseases, and Invasive Plants unit.

In 2014, shortly before Starkville’s termite team was transferred to the Forest Products Laboratory, Ulyshen moved to the Insects, Diseases and Invasive Plants unit in Athens, Georgia, where he received his PhD in entomology from the University of Georgia (UGA). In 2009, he was recognized by the Georgia Entomological Society as the Outstanding PhD student.

“I am excited to be here,” Ulyshen said. “I recently became an adjunct faculty member in the entomology department at UGA and will be working with several graduate students.  I had always secretly hoped to get back to Athens at some point, but never really expected it to happen.”

After he finishes up several projects from his time in Starkville, Ulyshen will focus his research on invasive insects. “In addition to applied research, I am interested in studying how communities of invasive insects and plants interact to impact forest biodiversity and function,” he said.  “I also hope to do some pollinator research.”

Ulyshen traveled  to Washington, D.C. on February 23rd to receive his award from Jimmy Reaves, Forest Service Deputy Chief for Research and Development.

For more information, email Michael Ulyshen at mulyshen@fs.fed.us

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Posted in Insects and Diseases, Threats