The Mexican monopoly on exporting invasive alien species continues. This one, popularly known as the Mexican Devil or the Crofton weed, is competing hard with its other comrades-in-invasion (the ecology demolishing squad!) and with near universal success. It is also known as the sticky eupatorium or sticky snakeroot. This noxious weed has spread across much of the tropical and sub-tropical world including China, India, Sri Lanka, Southeast Asia, Australia, New Zealand and the Pacific islands. South Africa is smitten by this weed and the USA has not been spared either. In India, beginning with the North East, it now appears to have spread elsewhere too, and found deep inside the Eravikulam national park in Kerala. The Mexican Devil can be seen in many agricultural and forest areas in Himachal and is commonly referred to as ‘Eupatorium’, its old name.

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Ageratina adenophora Spreng. The Mexican Devil

Like devils everywhere, this one too seeds profusely and then spreads far and wide; riding the wind, floating on water, piggy backing on animals and hitch-hiking along roads. Being a perennial, herbaceous shrub, Ageratina adenophora does not go away easily and tends to occupy after invading.

pic 2In Nepal the weed is known as “banmara” or killer of the forests. It quickly spreads in forest plantations, needing light to germinate and establish, but once that happens, the weed can grow in shady conditions by increasing its leaf spread to capture more light. In Kangra (Himachal Pradesh), the weed is generically called BUTI – meaning ‘plant’, but this could refer to other plants too? It is also called ‘cypress weed’ in India.

The spread of this weed into warmer (lower?) temperate areas of the Himalaya (up to and maybe above 2000 mts.) is a major reason for worry. As one drives along the Jogindernagar – Palampur road, the presence and spread of the Crofton weed on both sides of the road becomes apparent. In the last few years, this weed has alarmingly dispersed deeper into the Chil forests and it is anybody’s guess how much area within and outside forest is infested and spreading with the Mexican Devil. With temperatures predicted to rise to over 20C (could be more in specific locations in the mountains) due to global warming, the rapid spread of Ageratina into new territory seems assured.

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The introduction of the gall fly into India, a biological agent to check the growth and spread of Crofton weed and its subsequent spread to Nepal, has apparently had some effect, but over time is reported to have become less efficacious now. Systematic studies and monitoring especially due to impacts of climate change on this and other invasive weeds are the need of the hour – something that is not even remotely near the agenda for action; not in the COP21 Paris agreement anyway!

Crofton’s weed or the Mexican Devil is often confused with cousin – Chromolaena odorata (Devil’s Weed). Cousin of course is far more notorious an invader and figures among the 100 top invasive species of the world. From tropical Americas, the Devil’s weed has spread and naturalized in much of the Tropical world including many parts of India.

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Chromolaena odorata (L.) R.M. King & H. Robinson; synonym Eupatorium conyzoides Vahl.

The Hindi name of cousin – Bagh Dhoka – is most apt, tellingly identifying an invader that readily ‘ambushes’ the innocent native flora. And in Malayalam, Communist pacha seems to be even more appropriate! The unholy weed having sprung up from nowhere and all over God’s Own Country! And, the Irula antediluvian name ‘Madras Poo’ perhaps takes the cake!

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1 Comment

  1. says: Suma Tagadur Sureshchandra

    I really liked the title of this write up ” ALIEN INVADERS – IV”. Study to understand the effect of climate change, invaders ambushing original flora to be initiated. In some forests these aliens have wiped out the original flora, where ever I have visited or surveyed.

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