Category Archives: invasive species

Butterflies on Noxious Weeds

As I mentioned in my last post, regal fritillaries are out in high numbers in our Platte River Prairies.  We’re watching – among other things – what plant species they’re using for nectaring, and are interested to see if that use is similar to what we saw last year.  Right now, the most attractive plant to fritillaries is one that might surprise you – musk thistles.

On the other hand, if you’ve spent much time watching butterflies, you’ll not be too surprised at the attractiveness of this noxious weed to butterflies and other pollinators.  Native thistles are recognized as important nectar sources, but non-native thistles, especially those we’re legally obligated to eradicate, don’t always get the same positive attention.  This week our technicians were out looking for both musk thistles and regal fritillaries (for different reasons) and they were finding both simultaneously!  We ended up killing a lot of thistles out from under butterflies.

Here is a selection of photos from last Friday, showing fritillaries getting what they can out of these noxious weeds before we kill them off (the thistles, not the butterflies…)

It seemed like every musk thistle had a regal fritillary on it…


This fritillary flattened itself against a strong wind gust.

Alien Intruders Threaten Smokies’ Native Species

Published: August 8, 2009

CHARLOTTE, N.C. — Like an island, the leafy wilds of Great Smoky Mountains National Park lie anchored in a sea of tourist kitsch, power-plant pollution and vacation homes. And, oh, what the waves wash ashore.

From wild hogs to hemlock-killing insects to city lights polluting the night sky, the park’s worst environmental problems invade from outside its borders.

That locks park managers in a never-ending fight to protect and restore native species while fending off intruders. Now celebrating its 75th year, the park covers a half-million acres in North Carolina and Tennessee and is worldrenowned for its diversity of plants and animals.

“My primary challenge is to preserve the park ‘unimpaired’ for future generations, and that’s a pretty big word,” says Superintendent Dale Ditmanson.

When air pollution from far-flung smokestacks smothers mountain views, he adds, “I can’t send a ranger out to fix that.”

Nor can supervisory forester Kristine Johnson stop the devastation of Eastern hemlocks, the Smokies’ towering sentinel trees. The hemlock woolly adelgid, an Asian bug the size of one letter in this sentence, is killing trees 500 years old.

Johnson’s crews save some infested trees with insecticides and release beetles that prey on the adelgid, but the park holds far too many hemlocks to treat. While trees at higher altitudes are showing surprising resilience, the stands on mid-mountain slopes turn steadily grayer.

If most die, as appears likely, it will become the Smokies’ second epic disaster from an exotic source in recent decades. Until the 1940s, the white flowers of American chestnut trees covered the park’s slopes like snow. An imported fungus killed them all. Hemlocks are now only the highest-profile casualties. Of the 1,663 flowering plant species in the park, 380 don’t belong there. Fifty — multiflora rose, privet, Japanese honeysuckle, Oriental bittersweet — are aggressive enough to choke out native plants.

Park staffers inspect sources of gravel and topsoil, in which exotic plants might hitch rides into the park. They urge campers not to bring firewood into the park from 12 states where tree-killing insects are at work.

They can’t, however, make each hiker wipe his feet before entering. Muddy boots carry the seeds of invasive garlic mustard and coltsfoot up the Smokies’ slopes.

But every war has its victories. A little jewel of a fish, the brook trout, gave the Smokies a triumph of the natives.

Brookies’ story, like that of many species in the park, goes back 10,000 years to the last ice age. Trout were among the plants and animals that moved south as glaciers advanced, then were left stranded in the highlands when the ice receded.

Heavy logging early in the last century ruined many trout streams. By the 1970s, park biologists realized that air pollution was turning high-altitude water acidic. Non-native rainbow trout — the park had stocked 1.8 million over the years — were moving up streams.

Squeezed from above and below, brook trout had lost 70 percent of their range.

Now years of hard, expensive restoration work are paying off.

Park crews use chemicals to kill rainbows in streams. Then they capture brook trout, sometimes hiking miles across steep slopes with the fish in water-filled backpacks, and release them in the newly cleared streams.

The park now has 120 miles of brook trout water and plans to restore an additional 20 to 25 miles. In 2007, for the first time in three decades, the park allowed anglers to once again fish for brook trout.

There’s a reason so many non-native plants thrive in the Smokies: It feels like home.

The park’s diverse terrain, from river bottoms to some of the highest peaks in the East, mirrors the native habitats of many of the invaders. Most of them were brought to the United States as ornamental plants.

“We have places that are like South Africa, like Canada, like Europe, and many places that are like China,” Johnson says.

The Southern Appalachians’ frequent rains and many streams provide niches where non-natives can survive, adds Gary Kauffman, a U.S. Forest Service botanist in Asheville, N.C.

The moist conditions make it more likely seeds will germinate when soil is disturbed by logging, road construction or falling trees, he said. Non-native plants spread especially quickly along streams, which can carry seeds, stems and roots long distances.

Once established, exotic plants often don’t face the diseases, parasites or harsh climates that keep them in check at home, and they can choke out natives.

Their nationwide impact, in reduced crop yields, lost livestock range and extra lawn and garden maintenance, is an estimated $50 billion a year. When the invaders weigh as much as a grown man and wear long, curved tusks, the park turns to more assertive control techniques.

European wild hogs, covered in coarse hair, escaped from a North Carolina hunting preserve in the 1920s and spread into the Smokies. Consummate survivors, the hogs rototill the ground with their tusks as they grub for food, trampling rare plants, gobbling salamanders and fouling streams.

A heavy crop of nuts last fall only magnified their prolific reproduction. So far this year, park crews have trapped and killed more than 500 hogs, the biggest number since 1987.

“We know that, like the hemlock woolly adelgid, we’re never going to get rid of them,” said park spokesman Nancy Gray. “But we’re trying to keep their population stable.”

Last year’s bumper crops of nuts, berries and cicadas also gave a boost to a Smokies native species: the park’s 1,500 black bears. Sows that normally give birth to two or three cubs were spotted with four to five this spring.

The park had to close five backcountry campsites where hungry bears ripped into tents. They twice closed a trail near popular Cades Cove after a bear threatened hikers. The most-visited national park even guards its dark nights and serene quiet.

Development nibbles at the park’s edges. By 2002, the little town of Gatlinburg, Tenn., housed 407 stores, hotels and motels, restaurants, real estate offices and entertainment venues, one for about every 10 residents.

Two years ago technicians installed high-resolution cameras atop the tower of 6,643-foot Clingmans Dome, the park’s highest point, and began recording background brightness levels in the night sky. Monitoring of soundscapes, separating the rush of waterfalls from the honk of car horns, also began.

The work will serve as a baseline for future comparisons.

Animals, such as night-hunting owls, need darkness and quiet as they do food, water and shelter, said Jim Renfro, a park air-quality specialist. So do people.

Look up on a clear night, he said, and it’s still possible to see the Milky Way and stars. But the horizon glows, high into the sky, with the earthly light of the Tennessee Valley, Asheville and Atlanta.

Invasion in the Badlands

On vacation in the Badlands and Black Hills of South Dakota, I witnessed another invasion of beautiful ecosystems. Angry for several days and feeling helpless to do anything about the Yellow Sweet Clover marching over the landscape, I told my wife, Donna that I had to do something to alert people to this takeover of these beautiful landscapes. After several nights, I thought about how over the past 60 years I have been aware of invasive species and have seen the list grow and grow and grow.
What is our place on this planet? Does our labeling of plants as negative aliens and as invaders invite more negative thoughts? What good has become of our waging war on these alien species? Shouting and preaching that this just isn’t right nor nature’s way and getting all fired up and angry at one of God’s creations just didn’t seem to fit well with me anymore. I’m tired of generating negative feelings inside of me. This thought made me start to question the overall picture of man and nature and our relationship to plants, each other and our interaction with all species of our world.

Here are some of my questions that I ponder often:
· Were any species created out of negative thoughts?
· Were any plants or animals meant to remain in one area? If so, why do they do so well when introduced into different areas?
· What is the long-term succession of these so-called invasives or alien species? I mean over thousands of years?
· Can we live with these aliens and make peace or will we always wage war on them?
· Does the attack on the “invasive species” ultimately do any good?
· Are we supposed to sit back and do nothing?
· Can we make any peace with this rapidly changing world of the intermingling of species?
· Is this really a natural event and man truly is a part of nature but thinks that he isn’t because of his ability to choose and reason?
· Is it logical to think that man isn’t a part of nature or is this just another arrogant thought that puts us as the ultimate animal separated from all nature and we stand alone still fighting and compartmentalizing all species.
· Is there a kinder, more positive and cooperative way of dealing with what we perceive as invasive species?
· Does prejudice produce more prejudice?
If we are just holographic pieces of the “Great Spirit”, then we are included in this great magnificent process that created the universe and all within it. Are we not programmed to keep creating something different?
Does any one thing deserve to be eradicated or is that part of the plan?
Are the invasives just signals to us that we need to change our ways and they are just messengers sacrificing their lives for a cause yet unknown to us?
Some of the species that I have come into contact with and waged war over the years are:
· Japanese Honey Suckle
· Kudzu
· Multi-flora Rose
· Crown Vetch
· Yellow Sweet Clover
· Garlic Mustard
These are just a minute number of species that I have allowed to cause stress and negative energy in me. I think that now after decades of fighting, I am ready to accept that these aliens are just part of the cosmic progression to a different place on earth and the universe that is neither good nor bad.
What do you think?

Tired of struggling over this issue,
Howard Bright President Ion Exchange, Inc.

Munching on Garlic Mustard

A New Weevil in the Works

Garlic and mustard are common ingredients that can be found in American households. But garlic mustard? Well, that’s a different story.

Garlic mustard, Alliaria petiolata, is considered one of the most problematic invaders of temperate forests in North America. According to legend, it was brought here from Europe in the 1860s as a culinary herb, but unfortunately, it doesn’t taste very good. Since then, garlic mustard has spread to 34 U.S. states and 4 Canadian provinces.

“Garlic mustard is an invasive plant that gets a lot of attention,” says ecologist Adam Davis, who has been studying the weed for years. “It’s very noticeable and hard to eradicate because of its seed bank.”

The term “seed bank” refers to seeds in the soil that are dormant but capable of germinating. Garlic mustard seeds can remain viable for more than 10 years. A single plant can produce hundreds of seeds, which scatter as far as several meters from the parent.

“You can spend a lot of time and money pulling garlic mustard up or spraying it with pesticides, but it’ll just come back the next year,” says Davis. “That’s why it’s such a problem. It’s very resilient.”

Flowers of garlic mustard produce up to several thousand seeds per plant, making it difficult to control.

A member of the mustard family Brassicaceae, garlic mustard got its name because its leaves, when crushed, smell like garlic. Garlic mustard is a biennial plant, meaning it takes 2 years to complete its life cycle. During its first year, the plant is in the form of a rosette with kidney-shaped leaves that remain green throughout the winter. In its second year, the plant matures and produces small, white flowers, each with four petals in the shape of a cross. The mature plants either self-pollinate or are pollinated by insects, producing seeds that fall to the ground and enter the soil.

Garlic mustard is cold hardy and shade tolerant, enabling it to grow early in spring when most plants are not able to grow. It also secretes allelochemicals into the soil. Allelochemicals are chemical compounds a plant introduces into the growing environment to suppress growth of another plant. “It’s kind of like chemical warfare against the native plants,” says Davis.

The insects and fungi that feed on garlic mustard in its native habitat are not present in North America, increasing the weed’s seed productivity and allowing it to outcompete native plants.

In Urbana, Illinois, ecologist Adam Davis records the position of garlic mustard rosettes (clusters of green leaves low to the ground) on a sheet of transparent mylar. The locations are recorded in June and October of the first year and in June the following year to estimate rosette survival rates.  Once garlic mustard rosette locations are recorded, they are then converted into digital coordinates in a GIS (geographical information system) program, permitting spatial analysis of rosette survival.

A Model Solution

To better understand garlic mustard and find a suitable biocontrol, Davis—in collaboration with colleagues at Michigan State University, Cornell University, the University of Illinois, and the Centre for Agricultural Biosciences International (CABI) in Switzerland—created a computer model that simulates the weed’s life cycle.

“In part, we wanted to answer ecologists’ criticisms that biocontrol can potentially cause as many problems as it solves because of unintended consequences,” says Davis. “We were looking for a way to choose agents that are most likely to succeed while reducing their potential for harm to native plants and environments. Ideally, we want to try to release only one organism, if possible.”

Through this model, Davis was able to predict the type and severity of damage that would be needed to reduce garlic mustard’s population growth rates. Davis performed an analysis using computer code that enabled him to change one variable at a time while keeping all the others constant, allowing him to probe the life cycle for the plant’s weak point. He found that in order to make an impact, a biocontrol agent has to reduce garlic mustard’s survival in the rosette stage and its ability to reproduce in the adult stage.

Well before Davis created the life-cycle model, CABI scientists began looking for and testing potential biocontrol agents to tackle garlic mustard. They collected data on the amount of damage each insect could inflict on the garlic mustard population. From a list of more than 70 natural enemies found to be feeding on garlic mustard in Europe, four Ceutorhynchus weevils were selected as the most promising control agents.

Combining the feeding information collected by CABI scientists and the demographic information of garlic mustard in North America, Davis used the computerized life-cycle model to assess each weevil’s ability to inflict damage on the weed and inhibit its growth. One weevil, C. scrobicollis, came out on top.

High Hopes for Little Insect

The tiny C. scrobicollis has a life cycle of 1 year and produces one batch of offspring per lifetime. Itlays its eggs on garlic mustard’s leaf stems in the fall. When the eggs hatch in the spring, the larvae feed on the weed’s root crown, the area from which the rosette’s leaves grow and where nutrients are stored.

By feeding on the root crown, C. scrobicollis stops the flow of nutrients and water from the roots to the rest of the plant. It also damages the meristem, the area of the plant where new growth takes place. As a result, garlic mustard produces fewer seeds or, in areas with high weevil populations, dies prematurely in early spring without producing any seeds.

C. scrobicollis also appears to be monophagous, meaning it eats just one thing: garlic mustard. That means scientists won’t have to worry about any unintended consequences when using this insect as a biocontrol agent.

During preliminary testing, CABI scientists believed C. scrobicollis was the best candidate to control garlic mustard. Putting the weevil’s feeding data through Davis’s life-cycle model confirmed their beliefs and created a stronger case for the permit process.

“The model gave teeth to the permit application to release this weevil in the United States,” says Davis. “It provided a peek into the future as to the impact the weevil could have on the garlic mustard population here.”

C. scrobicollis is currently in quarantine at the University of Minnesota. If all goes well, this beneficial weevil may soon be roaming North America to find a nice garlic mustard meal.—By Stephanie Yao, <> Agricultural Research Service Information Staff.

This research is part of Crop Protection and Quarantine, an ARS national program (#304) described on the World Wide Web at <> .

Adam Davis <>  is in the USDA-ARS Invasive Weed Management Research Unit <> , 1102 S. Goodwin Ave., Urbana, IL 61801-4730; phone (217) 333-9654, fax (217) 333-5251