Invasive species control : 10 posts by 7 authors.

Recently I came across a post of Dendrobium barbatulum growing on Acacia. So I felt like writing about it.
There are many ways to look at it, but ultimately it is not a happy moment in anycase.
 
Orchid seed germination is strictly dependent on fungal association, so growing on Acacia means it was able to find a fungi (mycorrhiza) that was able to grow on Acacia which is native to Australia. Question is, did the orchids adapt to a new environment or the fungi?
 
Many times we walk in the forests and even if we are very much careful and we dont wish to disturb the natural environment, we do throw things like fruits and vegetables (left overs from our food) saying that it is biodegradable. But can you imagine, an apple doesnt grow in the western ghats, then how does the apple get decomposed there by a fungi or bacteria? Microorganisms are everywhere, they just need a host to propagate. An apple decomposing fungi or bacteria cant propagate if there is no apple and hence no apple tree in the area is a kind of a biocontrol for that fungi or bacteria etc. But its human who alters the environment every where. Even by throwing a bio degradable apple on the floor in a non apple area, we are kind of adding very minor doses of poison to the environment there and its not good for natural habitat.
Ever thought, how a pig virus that was supposed to infect only pigs could infect human being causing swine flu? Its not the adaptation of human but the microorganisms.
Just somethings to ponder about!! and we must not encourage exotics to take over natural vegetation in India.
Few days back I was attending one seminar by a guy from China. He is one of the two persons who manages the online Forest Herbarium database. People from all over china just upload their pics selflessly (something similar to what we do on efloraofindia). They also keep tracks of the exotic or alien plants. Recently they came across an invasive climber of Mikania which was uploaded by one of the citizen scientists for id. It was the first report of this invasive species from a particular county or area. Hence it was reported to authorities and they went to the concerned area and destroyed all individuals of this invasive species. India must have a proper invasive species management system before Lantana reaches the top of himalayas.


Very interesting information and good thought. We environmentalists talking many things doing nothing some times.


Well written …!
Invasive Alien Plant Species are second worst threat to biodiversity. Lantan camara, one of the 100 worst weeds of the world, has already reached up to 2000m altitude in areas of Uttarakhand. 10th Feb issue of Current Science have a report of a new and menacing weed Ambrosia psilostachya DC (Asteraceae) establishing in Tumkur district Karnataka. It is to be seen that whether we also eradicate it immediately or allow it to rob all the crop fields and native vegetation.


… wrote,

Few days back I was attending one seminar by a guy from China. He is one of the two persons who manages the online Forest Herbarium database. People from all over china just upload their pics selflessly (something similar to what we do on efloraofindia). They also keep tracks of the exotic or alien plants. Recently they came across an invasive climber of Mikania which was uploaded by one of the citizen scientists for id. It was the first report of this invasive species from a particular county or area. Hence it was reported to authorities and they went to the concerned area and destroyed all individuals of this invasive species. India must have a proper invasive species management system before Lantana reaches the top of himalayas.
I say, this can happen in China but not in India.
If it happens here than it will be a miracle, although miracles do happens but very very rare in present working force in India.


Thanks … for the thought-provoking note. I fully agree that there should be an effective management of invasive obnoxious species.

I feel that quarantine measures must be more strengthened in order to curb the entry of obnoxious weeds. Few years back we observed an emerging population of Acanthospermum australe (a new weed to India), in Bangalore, Karnataka. We presumed that this could have entered through imported poultry feed. Import of such materials and other seeds should be strictly quarantined.


… after reading you informative post i feel like sharing this

At my place Choromolaena odorata has eaten up so many other beautiful plants
we call it ‘Ran modi’ in Marathi meaning forest destroyer … destructive invasive weed
On the top our Intelligent Forest Dept. is cultivating Acacia auriculiformis plants all over road side in forest .. instead of eradicating them
I have found Dendrobium barbatulum growing on one of them
Acacia auriculiformis, Chromolaena odorata , Lantana camara are having allelopathic effects destroying other plants
It just came in to my mind ..is it possible to eradicate them completely?
Can luxuriantly growing weeds like Chromolaena odorata be destroyed by aerial spray of some target specific weedicides?


With use of controlled weedicide, all herbaceous and some shrubby weeds can be destroyed. But it has to be done on a very large scale. But some people may not prefer chemicals.
There must be some biological controls too, just that we need to do some research. For example, find a catterpillar that feeds exclusively on Chromolaena sp. Once the plant is extinct from area, that particular catterpillar will also go extinct on its own.
Third way is to organise a megaevent to uproot all these weeds one by one.
Where there is a will, there is a way.


Dear …  and friends

Thanks for the responses.

Before understanding why Orchids are accepting exotic hosts, we should understand the germination process of Orchid seeds.
Orchid seeds lack endosperm which in normal seeds act as a source of food for the developing embryo. Hence orchid seeds need to be associated with the specific fungi (mycorrhiza) for nutrition during their germination. Later they need association of other set of fungi which are usually endophytic. Seed germination is a very peculiar and tough stage but once the orchid seedling is bigger they can usually grow in nutritive condition which can be created due to debris around the roots etc.
At the same time to understand the growth of fungi, fungi needs specific hosts too to grow, some are very specific and some can grow on more than one host where as the third group generalist and can grow on many kind of hosts.
Orchid seeds when dispersed need a kind of platform where they dont get washed or blown away. The fissures and cracks on the bark of host trees create such ideal place for an orchid seed to sit in stable position. Then they need a particular fungi with which they can form associations. If an orchid is native to India, then it obviously means that the fungi with which it will get associated is also found in India in and/or around the same locality. Both orchids and fungi are a bit adaptive to the new environment (fungi is more adaptive). So if you plant a native tree then it helps in regeneration of the existing fungi that can be found on the bark. But if you plant an exotic tree then its not an ideal habitat for the fungi, although the cracks in the bark would be a good place for orchid seeds to sit. So if an epiphytic orchid is able to GERMINATE on a non native tree then it means that the fungi was able to adapt itself to grow on the non native tree as well. This can happen if the fungi is a generalist and can grow everywhere or IT ADAPTED to the new bark.
If a fungi and other microbes keep adapting to a new environment (created by exotics) then its likely that they will loose adaptability to the original native habitat on a long run. This is when it gets tricky. During current trend it is believed that all seed plants come in association with a fungi at one point of their life, in some manner and this association form a critical part of their life cycle. In some seed, the seed coat needs to be decomposed for the cotyledons to emerge out. If such fungi goes extinct then the such seeds will never germinate.
At the same time fungi and other microbes help in decomposing the dead organisms too. Imagine if they loose their adaptability to decompose. We say the plastic takes 70 years to decompose. Can you imagine without these microbes you cant even decompose a small apple !! forget about the kitchen waste which we collect every day.
So the bottom line is, dont add anything exotic to a natural environment, not even in the name of it being bio degradable. By adding them we are adding poison to our natural environment in small doses and one day it will accumulate so much that we will loose the natural environment.


This was a wonderful narration about the behaviour of Nature which is very interesting. These associations are amazing.
Regarding the last point about mass uprooting : I remember during our school days in 70s we were taken to open spaces to uproot the weed Parthenium. It seems to have worked to some extent. We had a massive drought and red coloured sorghum(Milo) was imported for food probably from USA. The parthenium seeds came through it probably.


Yes I agree with u Pankaj biological control is best way of eradication such luxuriously growing weed

Satish sir, i wish mechanical method.. up rooting by hand.. used for Parthenium, would be used before establishment Chromolaena tpp
but the weed has now covering huge area ..out of control
At my place they are burning Chromolaena, after it is dried which hardly affects population of weed but affects near by trees and other plants for sure
Dry season plus heat produced by burning of weeds, i feel so sad for tees…
… i have tried to stop them… but no use 🙁
I am going to write forest dept about this


Biological control of weeds : with respect to discussion on invasive  … has sent me link

which gives information about research done on biological control of Chromolaena odorata and other weeds
i sharing on her behalf bcoz she said she is willing to share it on eflora but her internet connection has got some problem
Thanks … for link

 
 
 
 

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