Biological Control of Ipomoea carnea the aquatic weed

A series of workshops on "Biological control of 'Ipomoea carnea' (Neyveli kattamanakku in Tamil) and Water Hyacinth 'Eichhornia crassipes' (Aagaya thamarai in Tamil) for sustainable irrigation management and environmental conservations" were conducted by Agricultural and environmental research stations of Tamilnadu Agricultural University in many stations, catalyzed and supported by the 'Tamilnadu State council for Science and Technology'.

Ipomoea carnea (Neyveli Kattamanakku in Tamil)
Picture courtesy: Wikipedia

Seed of Ipomoea carnea: (Picture courtesy: Wikipedia)


Water Hyacinth 'Eichhornia crassipes (Aagaya thamarai in Tamil)
Picture courtesy:TNAU Agritech


I happened to attend one such meeting which was presided by the District Collector wherein various methods to control the spread of this highly invasive weed was discussed.

Manual removal and mechanical removal of Ipomoea carnea is not possible because of so many factors such as man power availability, cost involved, clearing operations in muddy ponds and water ways and the main problem of weed regrowth in a very short time.

Chemical control (spraying weedicides such as 2-4D, Glyphosate Etc.,) though effective to some extent can not guarantee the re emergence of this highly proliferating aquatic weed. Even though these toxic chemicals are sprayed on the floating plants only, some amount of weedicide gets mixed with water leading to death of fishes and other aquatic organisms. Water from such ponds should not be used for irrigation as this is extremely harmful for the cultivated plants in the hapless farmer's field. To put it simply, adopting this control measure is an environmental hazard.

Waterhyacinth is the native of Amazon, introduced into the river Hoogly, in India by the Queen Victoria when she visited Calcutta during the British rule. At that time her intention was to beautify the river Hoogly like that of Thames in London.

This exotic plant doubles in 10 days and we are now witnessing large, floating mats of waterhyacinth in every ponds and rivers, obstructing navigation, clogging irrigation channels and most importantly acts as mosquito breeding ground. It is estimated that 200 tons of this weed can be harvested from an acre year after year. Such is it's amazing rate of growth.

In order to control the growth of these weeds, scientists all over the world are studying and utilizing the following organisms which feed on these aquatic weeds.

• Water hyacinth Weevils
• Water hyacinth mites
• Fish ( Grass carp)
• Pond snail
• Grass hopper
• Fungi
• Snail(Pila globosa)

Out of the above identified organisms the 'Water hyacinth Weevils' namely 'Neochetina bruchi' and 'Neochetina eichhorniae' are found to be more effective to control the spread of this Water hyacinth namely Ipomoea carnea.


In the picture N. eichhorniae is in left, N. bruchi is in right. (Picture:Cornwell University)

Their habitat is water hyacinth, they feed on water hyacinth and their whole life cycle is within the water hyacinth weed only. Although declines of these waterhyacinth populations were well documented by the scientists and readily attributable to biological control, the documentation was never published. (Source:Cornwell University)

So for good to hear. Isn't it. Now the worst part!

Don't think the above two Waterhyacinth feeders' are native of India and can be multiplied in labs for distribution among farmers. The 'Tamilnadu State council for Science and Technology' has already imported these weevils from U.S for multiplication trials.

So, we are in a awful situation where in we are going to face a (purposedly introduced foreign) pest, to control an earlier introduced highly invasive pest called Ipomoea carnea.

We all know that any harm to the ecology, whatever little it is, can not be reversed.

Their argument that these weevils feed only the water hyacinth and will fast to death once the availability of waterhyacinth ceases, has no proof at all. What we are going to do if these weevils jump to our food crops? Insects are highly adoptable in nature and the mankind has not eradicated a single insect so far after billions and billions tons of pesticide usage is itself an ample proof.

So, our scientists and the Govt. has to think of other constructive ways as listed here under to control the spread of this dreadful weed for the environmental safety:

• Bio degradable plastic from Ipomoea carnea. (Dr.A.G.Murugesan of Sri Paramakalyani centre for Environmental sciences, Alwarkurichi, Tirunelveli has got national award on this study)
• Ipomoea carnea compost.
• Ipomoea carnea + Vermicompost.
  
• Ipomoea carnea + Poultry waste compost.
• Ipomoea carnea leaf extracts as pest repellent.
• Ipomoea carnea for paper industry.
• Ipomoea carnea for Biomass power Energy plants.

Note the TNAU findings :

• Composted Ipomoea carnea plants can be used as organic manure preferably in rice fields.
• Vermi-composting and composting of dried water hyacinth and can be used as organic manure in irrigated upland ecosystems.

The above points were explained in detail to our District collector who accepted our view and canceled the trial of releasing Water hyacinth weevils in about 20 irrigation tanks in the district until further orders. The concerned scientist was asked to do more research and come with convincing results.

I came to know that in some Districts, Govt authorities had already released Water hyacinth weevils in irrigation tanks wherever the weed infestation is severe, without informing the local farmers.

I can only pray for our Mother earth's safety.

Regards,
Vishnu Sankar