African Invasive Plants “Destroying Livelihoods in Africa” – New Video from CABI

A new video from CABI “The Green Invasion – Destroying Livelihoods in Africa” plainly shows the devastating effects of four invasive plants in Africa. The four plants are parthenium (famine weed), opuntia (prickly pear cactus),

Prickly Pear Cactus

Prickly Pear Cactus

prosopis (mathenge), and chromolaena (devil weed).

CABI is an inter-governmental, not-for-profit organization set up by a United Nations treaty. Its “mission is to improve people’s lives worldwide by providing information and applying scientific expertise to solve problems in agriculture and the environment.”

Two things struck me about the video: first, because the people in the video are living close to the margin, you really see the effects of these invasives on their ability to survive; second, the video demonstrates how a plant such as prickly pear cactus can be perfectly well-behaved on one continent but a disaster on another.

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Deer Don’t Like Foreign Foods – Deer Prefer Native Plants and this Changes Forest Succession

Deer Browsing on Native Conifer, White-tailed deer browsing: http://lib.colostate.edu/research/agnic/images/forestry.html

Deer Browsing on Native Conifer, White-tailed deer browsing: http://lib.colostate.edu/research/agnic/images/forestry.html

For anyone who has spent time in forests where whitetail deer proliferate, this is no surprise: Deer prefer native plants. This leaves non-native plants to flourish and drop their seeds, thereby altering the seed bank. These are the conclusions of a recent study: “Deer Browsing Delays Succession by Altering Aboveground Vegetation and Belowground Seed Banks (free access).”

One of the authors, Antonio DiTommaso from Cornell states “It’s obvious that the deer are affecting the above-ground species, but it’s like an iceberg. There are major effects below the soil surface. We are seeing a divergence of seeds contained within the soil from what should be there. We’re seeing an escalation of non-native seed and the virtual elimination of woody plant seeds.” This will have long-term effects. “Deer are slowing down forest succession or natural establishment. In fact, the deer are preventing forests from establishing,” says Anurag Agrawal, Cornell professor of ecology and evolutionary biology, a co-author on the paper.

The one thing I don’t understand: the authors observed “the nearly complete suppression of woody plants.” What about woody invasives such as buckthorn, honeysuckle, and tree of heaven? I have never seen evidence of deer browse on these non-native woody species.

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Girdling Trees to Create Snags and Coarse Woody Debris and to Improve Wildlife Habitat

A dense overgrown forest provides poor quality wildlife habitat.  See, e.g., Knapp et al. 2013.  Dead wood such as snags and coarse woody debris are increasingly seen as critical to healthy forest ecosystems.  Bottorff 2009. Girdling a tree to create a snag accomplishes two goals: it thins a stand of trees, and it provides the dead wood essential to many species.  I also believe it is a much easier way to thin a stand of trees than conventional logging methods, especially for the land manager with minimal heavy equipment.

Scots pine snag

Scots pine snag

In this presentation, Girdling Trees to Create Snags and Coarse Woody Debris, I describe how we have managed a small woodland for the past several years where snag creation is a critical component of the management.  This is not scientific research, but the experience we have gained may be helpful to others.

What does this have to do with invasive plants? Not much.  I have tried girdling invasive trees like buckthorn (Rhamnus cathartica) with limited success.  In fact, I would generally not recommend girdling invasive plants because girdling usually kills a tree slowly and may allow ongoing seed production.  Nonetheless, just like invasives removal, snag and coarse woody debris creation is another way to improve habitat.

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Map of Invasive Knotweed Along Paint Creek in Northeast Iowa

If you want to see how knotweeds like Japanese, Bohemian, and giant, spread, take a look at this map: Paint Creek Japanese Knotweed. Richard Kittelson from Northeast Iowa Resource Conservation and Development extensively mapped the spread of knotweeds along Paint Creek in northeast Iowa. It’s a beautiful, hilly part of Iowa where small creeks and rivers run through hardwood forests and drain to the Mississippi.

Blackhawk Bluff along the Upper Iowa River

Blackhawk Bluff along the Upper Iowa River

Northeast Iowa Resource Conservation & Development (RC&D) and several partners such as the United States Forest Service and area landowners are implementing a three year initiative to control knotweed in the Paint Creek Watershed. The first part of their initiative was to map.

Knotweed at the headwaters of Paint Creek

Knotweed at the headwaters of Paint Creek

Altogether Richard found about 27 acres of knotweed in the 7 square mile area represented on this map. The vast majority of it was not planted by humans but spread through vegetative reproduction along Paint Creek. No doubt flood waters carried pieces of the stem and rhizomes downstream. The knotweed is represented by hot pink on the map and large sections of Paint Creek are bordered in hot pink.

In conversations that Richard had with residents, he found that knotweed was likely introduced by just a few local gardeners more than 30 years ago. Once the knotweed made it to the banks of Paint Creek, it spread on its own.

What is perhaps most concerning about knotweeds is that the vector that so readily transports it – waterways – also is vital habitat to wildlife. People who have seen knotweed along a stream know that once it gains a foothold, knotweed can form monocultures along the banks where nothing else can grow.

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Winter Invasive Plant Control – Five Reasons to Apply Herbicides in the Winter to Control Woody Weeds such as Shrubs and Trees

freshly cut buckthorn stump

freshly cut buckthorn stump

Foam herbicide applied to buckthorn stump

Foam herbicide applied to buckthorn stump

I did a post a few years back on doing winter herbicide applications on woody weeds.  When I mention winter applications, especially in northern climes, most people, even some experienced herbicide applicators, are skeptical.

There are two main misconceptions.  One is that dormant woody plants will not properly absorb and translocate the herbicide.  Herbicide labels often have a statement such as apply only to weeds that are “actively growing.”  While this may be true for herbaceous plants – you can’t apply herbicide to a dried up leaf – it isn’t necessarily true for woody ones.    The herbicide obviously needs to reach a living part of the tree or shrub.  In the winter if you are using an amine herbicide, this can be done by exposing the cambium using for example a cut stump application technique (as shown in the photos) and applying the herbicide.

A second misconception is that the herbicide will freeze.  I have used amine herbicides such as glyphosate with a water carrier in temperatures as low as 10 degrees F.  While the nozzle can occasionally freeze-up if you wait too long between spraying sessions, this rarely happens.  Generally, it seems the salts in the concentrated glyphosate formulation used for cut stump treatments keep the liquid from freezing.

But even if you can do it, why should you apply in the winter?  I would offer five advantages:

  1. Effectiveness.  I have had great success with winter applications using cut stump and frill techniques.  Others have too.  See Reinartz 2002.  I use a concentrated herbicide solution of glyphosate with between 20 and 25% active ingredient.  I also try to cut the stump or the frill as low to the ground as possible – two to five inches from the ground.  (So, don’t tackle applications in deep snow; it’s not worth it.)
  2. Reduced off-target harm.  You won’t have to worry – assuming you are in a temperate climate – about hitting the leaves of desirable plants.
  3. Ease of movement and identification.  It is amazing how much more open and accessible an area can be without deciduous foliage.  For identification, you just need to know the target plant’s bark and structure.  Fruit, such as buckthorn berries, which stays on through the winter can help you identify your target weeds.
  4. Comfort.  I am serious!  In the summer you are sweating excessively, especially with your protective clothing and equipment on.  In the winter, that extra clothing is appreciated.  As long as you wear layers that can be put on and taken off as activity levels change, you can be very comfortable.  Perhaps most importantly – there are no bugs; no ticks; no poison ivy; and no pollen (for those suffering from allergies).
  5. Enjoyment.  Getting outside on a sunny winter day – there really is nothing like it:  Taking a deep breath of crisp air; listening to the rapping of a woodpecker.  And, if you are burning a pile of woody invasives, you can warm up by the fire!

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Google Earth – Could It Help Determine the Distrubution and Abundance of Invasive Trees?

Google Earth Logo

Google Earth Logo

Researchers are proposing the use of virtual globes such as Google Earth for gathering data on the distribution and abundance of invasive trees. In their paper “Unlocking the potential of Goggle Earch as a tool in invasion science, Vernon Visser and colleagues suggest that Google Earth could help with early detection of emerging invasions, monitoring invasions over time, and identification of suitable field study sites. Not only might professionals use the tool but the authors believe that “citizen scientists” could participate in the effort. The article is published in the December issue of Biological Invasions.

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Invasion Scientists Respond to Invasion Biology and Invasion Ecology Naysayers and Skeptics

Are invasive species really a problem? Are they beneficial? A number of articles have appeared in the past few years in major journals and

Invasive species sign used by Washburn County, Wisconsin

Invasive species sign used by Washburn County, Wisconsin

well-respected newspapers questioning the legitimacy of the field of invasion science (also more narrowly referred to as invasion biology or invasion ecology). Some of these criticisms even call for the abolishment of invasion science or call it “irrational” or “deliberate persecution.”

Here’s a great (free) article that offers a comprehensive response to the skeptics: “Misleading criticisms of invasion science: a field guide.” The authors are David M. Richardson and Anthony Ricciardi. The authors have a helpful table where they list the six major criticisms  of invasion science along with point-by-point rebuttals.  Multiple sources are cited.

It would be wonderful to see a response to Richardson and Ricciardi. If there is, we will publish a follow-up article on it.

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