The 6th International Weed Science Congress at Hangzhou, China
- A report on Parthenium weed management -

Prof N Irabanta Singh *

The author recently attended the 6th International Weed Science' Congress (17-22 June, 2012) being organised by "The International Weed Science Society (IWSS)". About 500 Scientists representing 45 countries attended the six-day deliberations.

The Scientific presentation on Weed Science Congress consists of four key note addresses and twenty main topic viz-
1. Biology, dyanamics and ecology of weeds;
2. Integrated weed management in Arabic crops;
3. Integrated weed management in rice;
4. Integrated management in horticultural crops;
5. Integration weed management in plantation crops;
6. Weed management in crop areas;
7. Herbicide resistance in weeds and crops;
8. Biological control of weeds;
9. Site specific weed management;
10. Biotechnology, molecular biology and genomics as tools for weed management;
11. Weed management in organic farming;
12. Aquatic weed management;
13. Parasitic weeds;
14. Environmental aspect of weed management;
15. Natural products and allelopathy;
16. Invasive species;
17. Strengthening farmers capability for weed management in developing countries;
18. Plant management in areas of nature conservation;
19. Herbicide application and formulation and
20. Future challenges to agriculture and its impacts on weed science.

The author had presented the paper under the main topic - Weed Management in non­crop areas (Chairman, Dr. Come Kempenar, Netherland). The topic of oral presentation was "Invasive of Parthenium hysterophorus L. in North-East India and its Management". Parthenium hysterophorus L. commonly known as carrot weed, white top or congress grass in India, is an annual herbaceous plant belonging to the family Asteraceae (Compositae).

The origin of Parthenium hysterophorus L. is considered to be from semi-arid and sub-tropical region of America and has been accidentally introduced into India along with the imported food grains. After noticeable occurrence of Parthenium in Pune (Maharastra) in 1956, it has spread like a wild fire in almost every States of India.

At present, in India the weed has invaded about 35 million hectares of land which includes wastelands, crop lands and forest lands. P. hysterophorus is known to suppress local vegetation by release of growth inhibitors through leaching, exudation of roots, decay of roots, decay of residues, etc. It can affect natural diversity and caused extinction of native flora if it is not controlled at an earliest.

Parthenium hysterophorus L. posses a significant health risk to human being and toxic to livestock because of the presence of parthenium, a sesquiterpene lactone. Toxic effects include dermatitis and skin lesions, emaciation, rupture of tissues, haemorrhages in internal organs and caused death.

P. hysterophorus L. causes allergic reactions in susceptible humans. Symptoms include allergic eczematous, contact dermatitis through prolonged close contact with the weed and allergic rhinitis (hay fever) and allergic bronchitis through pollen. Manual and mechanical control of this weed is expensive and provides only short- term control requiring repeated applications.

On the other hand, biological control of weeds is a cost effective, environmentally safe "and ecologically viable method. Due to its prolific cover and hazardous properties of Parthenium hysterophorus L., adequate measures are needed for proper management.

The author and his team conducted regular field surveys of Parthenium growing regions of 12 National Highways (NH-31, NH-33, NH-37, NH-39, NH-44, NH-52, NH-53, NH-54, NH-59, NH-62, NH-62, NH-150) and 3 railway tracts of North-East India during 2009 to 2011. His team had used the integrated approach for the management of this noxious weed.

Different extracts of botanical agents like Gynura cusimba (D.Don) S.Moore, Amaranthus spinosa L., Mimosa pudica L., Cassia tora L,Cassia occidentalis L., Sida spinosa L., Riccinus communis L., Xanthium strumarium L., Chromolaena L., Urena lobota L., Mirabilis jalapa and Cassia sericea L.) were studied for their inhibitory effect on Parthenium.

Metabolites of Aspergillus niger var., Trichoderma viride Pers.ex.S.F. Gray, Penicillium sp, Fusarium oxysporium F. sp. ciceris (Foc), Alternaria alternate (Fr.) Keissle were also tested for their efficacy in controlling Parthenium and different stages of Zygograma bicolorata (Mexican beetle) were tested for their efficacy in controlling Parthenium.

Leaf and stem extracts (20% each) of Riccinus communis L., Mimosa pudica L. and Cassia tora L. showed 100% inhibition on Parthenium seed germination. The result show that Cassia tora L. Cassia sericea L, Xanthium strumarium L. and Amaranthus spinosa L. had maximum allelopathic effect.

Fusarium oxysporium f.sp.ciceris (Foc.) exhibited maximum inhibition on seed germination and seedling growth of Parthenium. The adult and larva of Zygograma bicolorata were found to "devour all the leaves of Parthenium except midrib significantly by reducing the height, shoot length, root length and biomass of Parthenium.

Work on Parthenium was also presented from other countries like Pakistan, Australia, USA and South Africa. The work include efforts towards the management of the invasive weed in Eastern and Southern Africa under the main topic "Integrated Weed Management in arable crops". From Pakistan three paper were presented under main topic "Invasive species and Natural products and allelopathy".

From Australia one paper was presented under the main topic "Invasive Species". On 19th June, 2012 the author also participated a workshop on Parthenium management through Global network In the workshop reports from countries like India, Pakistan, ShriLanka, Bangadesh, Nepal, Bhutan, China, Australia, Nigeria, etc. were presented by the representatives from the concerned countries.

Prof. S.W. Adkins, Queensland University, Australia is the Co-ordinator of the workshop. The future of Parthenium management in global perspective was theme of the workshop. All the participants feel to do further research for successful management of Parthenium through biological approach.

This International Congress on Weed Sciences throw a new light for future Parthenium management in North East India. The author thank Manipur University for travel grant.

*** Read more on this conference here