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Friday, February 22

North American weed spotted in India, could be major threat to agriculture and forests in future

If the initial hints are anything to believe, the farmlands and forests in India have a brand new invasive threat from a rarely reported foreign plant species native to North America. A recent research correspondence published in the Current Science journal claims to report the plant for the first time from India and argues that the plant can have tremendous invasive potential.

Western ragweed, Ambrosia psilostachya, invasive plant, north american weed, invasive plants in india, alien plants
Western ragweed (Ambrosia psilostachya)
Image courtesy: Krzysztof Ziarnek Kenraiz (Wikimedia commons)
 According to the researchers, the plant is presently reported from farm lands in the M. Bevinahalli village in Turuvekere taluk of Karnataka. On close examination and surveying the literature, the researchers were able to identify the new plant as Ambrosia psilostachya. Though the plant resembles its close relative Ambrosia artemisiifolia which is found in India, it is actually different, says the correspondence. 

Its Indian variety, Ambrosia artemisiifolia, was the only member of the genus hitherto reported from India. According to the correspondence, the new weed is native to North America and is known as perennial rag weed or western ragweed in North America.

New invasive plant threat in India
The research note warns that the weed has tremendous capacity to spread very rapidly and is known to cause allergic reactions in Humans. “If the weed is not controlled now, it may create a difficult to control situation once it proliferates from the location of present report”’ says the correspondence. 

According to the correspondence, the weed has not only invaded finger millet, mulberry, coconut and areca nut cultivation  but has also conquered the cattle pastures which have affected animal husbandry of these villages. The correspondence also notes that the plant has seriously affected local flora, by replacing local grass varieties, thus decreasing fodder availability. 

The plant is capable of spreading to large areas through extensive vegetative reproduction through underground rhizome like roots and stolon (part of the plant which makes new plant).  Though the plant has been present in some villages in Karnataka for the last 15 to 20 years, it is not yet clear what restricts it from spreading to other places.

 According to the researchers, since the plant does not have parts which supports seed dispersal through wind, the plant has not yet started spreading to other places. It is also not clearly known at this point if all the seeds produced by the plant are viable or if they exhibit any type of dormancy.

Though, there are not many issues reported about this plant expect its rapid invasion of farm lands in Karnataka Villages, reports from other countries indicate that the plant can cause allergic diseases in humans. “The species is said to be responsible for causing severe allergenic diseases in human beings in the United States”, says the correspondence.

The North American Connection
The plant is actually native to North America and the way in which it has reached Indian farmlands is still unknown. Though some speculates that the seeds could have been brought to India by migratory birds that use the seeds and other parts the plant for making nests, the connection is yet to be scientifically proved.
Though contaminated food grains are a usual way in which invasive plants reach farther places -as in the case of Lantana, a notorious weed in Indian forest- that may not be the reason for the spread of the present weed. “The introduction of the species through contaminated food grain may not be possible, as the weed is localized only in these villages in Karnataka”, says the paper.

The plant has already spread to parts of South America, Europe, New Caledonia, Japan, Taiwan and Australia. The researchers do not rule out the chances that the seeds reaching India from either of these places.

Weed control measures
 The presence of root buds, horizontally running rhizomes and dense root ramification makes the plant difficult to manage and eradicate. Periodical manual removal, shallow plowing before passing cultivator in farms has been recommended as a control measure. According to the note, if repeated control measures are taken, the weed can be controlled in 4 to 5 years from the country with its present restricted proliferation.

 M. T. Sanjay  and T. V. Ramachandra Prasad from the Directorate of Weed Science Research Centre, University of Agricultural Sciences, Bangalore, R. A. Sharma from Directorate of Weed Science Research, Indian Council of Agricultural Research, Jabalpur and R. R. RAO, from Bangalore co-authored the correspondence.

Read more on IBT's coverage on invasive species in India.


  1. Globalization means that it will be increasingly difficult to control such imports, voluntarily or accidently. This means, we shall also have a globalization of plant species with only those which are more invasive will be able to resist and expand all over the world?

    1. Dear Sunil,

      Thanks for the visit and comment. Though changes like globalization has, to some extent intensified, the introduction of new plants and animals in ecosystems not native to them, it is not a new phenomenon.
      Interestingly, the countries which are exponents of globalization themselves had made strict checks everywhere to make sure that such invasive species does not reach their soil. However, as you mentioned, it is difficult to stop them completely, as they are carried over by migrant birds and other similar carriers.

      Then, we strongly doubt that the idea of globalization of plant species will be disastrous since it will bring down the diversity of an ecosystem which will badly affect the survival of all other organisms in the ecosystem.that may not be a good idea for the good life on mother earth for long term.

  2. Nice article on this plant. Although, since the biodiversities of the US and India differ significantly. There are several varieties of plants that, otherwise considered invasive plants and weeds in other countries, that we are using in our gardens and other places for decorative purposes, for example, the california poppy(Eschscholzia californica) or the Raat Ki Rani(Cestrum Nocturnum) are considered invasive in the US and Australia, but here in India, we have these plants being sold in nurseries in specific seasons.

    1. Dear Cyberkid,

      Thank you for the comment.

      You are absolutely correct. Interestingly, many common species of plants and animals in our country are dreaded invasive species in other countries. Our common castor oil plant, Indian myna and mongoose are known invasive species in African and European countries. many plants which have reached our spoil through ornamental plant market has also caused the same problems.
      however, the invasive nature of a plant may differ from one place to another based many factors. The African cat fish when introduced as a profitable farm fish variety nobody doubted anything. but now it is a major invasive threat to the rich fish fauna of the Western Ghats Rivers.
      The western ragweed is a known invasive in many countries. it has been showing some invasive character in India also. so it will be better to keep an eye on it.

  3. This post suggests that Ambrosia artemisiifolia is native to India. It isn't. Ambrosia artemisiifolia is also a North American species and is considered invasive in Europe (and also in Japan, according to wikipedia).

    1. Dear Taka,

      Thanks for your comment and for adding additional information.

      You are correct. A. artemisiifolia is not native to India and it is invasive. It has indeed attacked japan also. (You may find a better source here).

      However, we would like to point out that we have not anywhere mentioned in our story that the plant is native to India. We have simply mentioned that A. artemisiifolia is the only plant from that genus to be reported from India prior to the spotting of the new plant.

      Even then, we understand that you have said something you felt as reader of our stories. We ask for apology if the story makes such a false impression that the plant is actually native to India.

      We appreciate the patience and care you have taken to make suggestions and improvements regarding our content. Thank you for that and we will be glad to have your comments on our stories in the future also.


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