To design the ideal control measure of invasive alien plants, the insights of the attached articles could help. The ground rules would be restoration of ground and canopy cover of the indigenous flora. In parallel, land management/ownership of the restored vegetation cover probably needs to be changed (burning; access and so on). The state is often not the ideal land manager. For canopy cover restoration, a non-evasive exotic tree species may be helpful in some cases as an intermediate step.

Indeed costly failure prevails.

Article Efficacy of Chromolaena odorata control in a South African c...

Article Invasion of an alien shrub across four land management regim...

One aspect missing in the question is neglect of social concern of the local people. Especially useful for the countermeasure invasive plants is to educate and informa local people on the invasive plant. If you are lucky you can eladicate them while they are low in abundance. If it spreads, then there is no longer possible to eradicate invasive species. Pease include social awareness explicitly in your planning.

Hello there!  I am not sure if your question is general, or targeted to a specific habitat or vegetation type (e.g., terrestrial, aquatic).  I deal with aquatic (freshwater) habitats.  The main invader in European freshwaters is a North American native (Elodea canadensis and more recently E. nuttallii), which have been extensively studied, but real, practical management plans are still in the wanting.  The applied aspects in this regard are in a more advanced stage of development in North America, where the there invasive Eurasian watermilfoil (Myriophyllum spicatum) causes problems similar to those caused by Elodea spp. in Europe.  Some research efforts have been put on the biocontrol of M. spicatum with native insects, after traditional efforts have failed (e.g., mechanical harvesting typically backfires because the plants regrow ever stronger from fully viable plant fragments).  The results from controlled experiments using herbivorous insects have been quite promising, then the results in the field have often been contradictory, with some success stories counterbalanced by failures.  The possible main culprit seems to be a native fish (a sunfish) which eats the plant-eating insects.  Research is still going on in this regard.  One of the leaders on M. spicatum as an alien invader in North America is Dr. Ray Newman at the University of Minnesota.  You can check the University's Minnesota Aquatic Invasive Species Research Center Website (http://www.maisrc.umn.edu/) for details and as a starting point for a quasi-complete bibliographic search.

-Paola

http://www.maisrc.umn.edu/

From a California perspective, it depends largely on exactly where the exotic plant species is invading?  Roadsides, railroads or utility right-of-ways, no money is usually spent on eradicating exotic species in those areas, so those are usually where new exotics get established first.  

Then there is a big difference between wild lands, pasture lands and cultivated fields in terms of how new exotic plants are treated or allowed to spread when they get introduced into those three areas.  Out of those three areas, only cultivated fields get any money spent, with the wild lands and pastures usually receive zero funds for exotic plant management.

Then if you are talking about eradicating a wild lands infestation, eradication alone is not a useful goal, because you usually leave a bare soil vacancy that can get easily reoccupied by another exotic.  

So you goal in a wild lands area, should be conversion of the exotic area back to a solid local native understory, like what I am doing in Palo Alto at http://www.ecoseeds.com/arastradero.html.  I am estimating that to convert the 70 acre hillside I am working in will ultimately cost about US$5-10 million, considering that the average cost of a home in the area is US$1 million.  

You can see where an attempt was made to convert two acres at the cost of $225,000 per acre by UC Davis and it took over 10 years and still not get to 100% conversion at http://www.ecoseeds.com/road.test.html. 

When you consider that the conversion from exotic plants back to original local ecosystems cost so much per acre or per hectare, even the wealthiest countries on the planet have only occasionally attempted this process, and only on very small experimental scales.  

Hi folks! One aspect I am usually misssing in most discussions on invasive plant species in f. e. Central Europe is the way these plants have made it into the ecosystem. Appart from the developement of globals unintentional transport like as contaminent in wastwater, garbage, etc., there is a permanent practically uncontroled source for plants: the trade. We actually have most problems with some nice decorative plants in Central Europe that have been brought into rural areas after beeing sold (and still are) in garden markets. Even if the problematic impact of such plants is known, no action has been taken yet to limit distribution via trade in most countries. This aspect has to be kept in mind when trying to run pest controle measures against invasive species too, as it obviously needs legislative assistance too!

Uwe

Working in woodland conservation in Scotland, one of the major issues I deal with is invasion by Rhododendron ponticum and its invasive hybrids.  There are many cases where control has been less successful than hoped - usually because of human factors, including:

• Work not being carried out properly in the first place
• insufficient follow-up - i.e. control of regrowth
• re-invasion from neighbouring land

Scottish Natural Heritage is working with Forestry Commission Scotland to create a comprehensive national strategy for controlling Rhodo, and I think you would be interested in a report published in 2013, which is available at http://scotland.forestry.gov.uk/images/corporate/pdf/rhododendron-control-review-2013.pdf. This is a critical review of the experiences and outcomes of past and current rhododendron control programmes, setting out how control has been carried out, what worked, what didn't, and why, and making recommendations for future control strategies.

Hello Nelson.

The attached study used an ecologically based control strategy to try to reduce recolonization by an invasive grass after it had been removed by hand and herbicide. We tried to increase competition from native plants by re-establishing native species, in a semi-arid environment. The efforts largely failed, probably due to particularly low rainfall reducing seedling establishment.

Whatever typically limits seedling establishment in your ecosystem, a recommendation is to increase your chances of hitting a good year for establishment by seeding or planting in several years.

Also, watch out for strategies that may actually favour the invasive species or damage established native plants. We found that planting seedlings increased invasive seedling emergence and increased native forb mortality, probably due to the increased soil disturbance that is inevitable when you plant out.

Persistence is important. Best of luck to you.

steve woods

Article An assessment of revegetation treatments following removal o...

Early action is necessary to stop many invasive exotics.  On the political side, I think agencies "in charge" of controlling exotics are not willing to go "all in" for eradication when an invasive exotic is first recorded.  I suspect much of this is because it requires regulation against the introducing entity and they're politically (and maybe financially) unable to institute regulation because of anti-government conservatism.

Two thoughts come to mind:

1)  It might be informative to flip the question and ask why the few successful eradication and control attempts have been successful.  Check out the literature on Caulerpa taxifolia in California for an eradication, with some good insights on why it worked (if you haven't already).  Certainly early detection and emergency funding availability were major factors, and were only possible because Caulerpa was already a known threat.  The area of first detection was also relatively easy to isolate.

2) While insufficient knowledge/planning/political will often contribute to failure, even successful eradication efforts may not improve the overall situation for native species, as has been noted by other contributors above with other examples.  Eradication of invasive herbivores on Pacific islands, for example, allowed invasive vines to proliferate.  Native plants on these islands are still threatened, now being out-competed instead of overgrazed.  There's some good discussion of this and related issues in - "Conceptual Ecology and Invasion BIology: Reciprocal Approaches to Nature" (2006) Marc Cadotte, Sean McMahon, and Tadashi Fukami are the eds. on that.  The resource is a bit older, but good for a start and could help ground some searches for you.

Good luck!  

Dear Nelson, 

I would say that the most important thing (after analyzing and controlling pathways of introductions) is early detection. However, sometimes failures in control of invasive species has been related to the cease of control measures, because they are wrongly believed to have worked. Consequently, have lead to a fast increase of the invasive species population again. This is usually known in the literature as the "lazarus effect" and you can find some nice examples in this paper: 

Scott A. Morrison, Norman Macdonald, Kelvin Walker, Lynn Lozier, and M Rebecca Shaw (2007). Facing the dilemma at eradication's end: uncertainty of absence and the Lazarus effect. Frontiers in Ecology and the Environment 2007 5:5, 271-276

http://www.esajournals.org/doi/abs/10.1890/1540-9295(2007)5%5B271:FTDAEE%5D2.0.CO%3B2

Also in:

Lockwood JL, Hoopes MF, Marchetti MP (2013) Invasion ecology (2nd ed). Wiley-Blackwell, Oxford, UK.

(See Chapter: Eradication and control of invaders)

Best wishes, 

Florencia

In Hungary, there are numerous agressive invasive alien plants. Two of them cause very serious problem in nature conservation by occupíing natural habitats: in wet, semi-wet and marshy meadow the Solidago (S. gigantea and S. canadensis) species  in forest and arid, semi-arid areas the Robinia pseudacacia.

 These  plants, now, are disasters for the natural habitats.

 Robinia was introduced into Hungary in the early 18th century. For 2014, Robinia occupied 470 thousand acres in Hungary (in 1885 it was only 24 thousand acres).  On the other hand., last year was an intensive public talk about to declare Robinia as Hungaricum or not (because of the outstanding quality of honey that it produce).

 There are plenty of papers studies on the unsuccesfull control of Robinia in Hungary, but unfortunately written in Hungarian since it is local catastrophe:

 http://www.okologia.mta.hu/sites/default/files/BARTHA_es_mtsai_Akac_attekintes_2014_vegleges.pdf

 In English it is also good, but far the most important the Hungarian one:

 http://link.springer.com/article/10.1023/B:BINV.0000005570.19429.73

 There is also a method for chemical control of  Glialka 480 Plus or Glyfos covering the cutted surface of Robinia trees,  but there is no possibility for countrywide introduction. Furtheremore it could stop only one reproduction form. 

 Also, because Robinia is a serious economic plant, only the control of its expansion is allowed but without any success.  

 Solidago. Mechanical control of these species looks like a "windmill battle". Even in nature conservation areas and national parks, the management is forced to introduce chemical control: namely 3% glyphosate. Which is able to produce short term and temporary results only.

 In English, you may find data here:

 https://www.cbd.int/doc/world/hu/hu-nr-05-en.pdf

 and also here:

 http://www.rougepark.com/unique/reports/RP_DSV_Report_Feb08.pdf

To Jeanette. I am familiar with Rhododendron ponticum in Ponticum and the British Isles. What is the problem besides being alien?

Hello Hein,

The problem with the invasive form of Rhododendron ponticum, is that it is extremely competitive, and forms a dense, tall (up to about 5m) understorey in woodlands, and a shrub layer on moorlands, that shades out pretty much all other plant species.  Trees cannot regenerate within it and nothing much grows underneath it except very common mosses such as Kindbergia praelonga.  Nothing browses it either, so there is really nothing to stop it spreading except human management.  Along with heavy grazing pressure, which prevents tree regeneration, it is the major threat to the bryophyte/ lichen-rich oceanic woodland communities of the west coast of Scotland.

Just to be clear, the Rhodo I'm talking about is not pure R. ponticum, (although this is the main parent species, and is the name generally used) but a complex hybrid with various other species including R. maximum and R. catawbiense.  This hybridisation seems to have increased its frost tolerance, so it survives well in eastern Scotland, which can get much colder than the west.  However, it does not spread as vigorously in the east as in the mild, humid climate of the west coast, so it is only a local problem - although still a serious one in some cases.

The name Rhododendron x superponticum has been proposed for the hybrid (Cullen, J. (2011) Naturalised rhododendrons widespread in Great Britain and Ireland.  Hanburyana Vol. 5 pp. 11-29), but I'm not sure how widely used this is. 

Jeanette