To combat a noxious weed like the Parthenium hysterophorus, a multipronged strategy that includes preventive measures, manual uprooting, herbicides and biological control agents is essential, said Dr AN Rao, Consultant, ICRISAT Development Center (IDC), at a recent seminar on “The menace and management of Parthenium hysterophorus”.
P hysterophorus, a flowering plant in the aster family, Asteraceae, is a highly invasive and aggressive weed.
“A single seed of Parthenium can give rise to up to 25,000 seeds, creating an enormous seed bank in the soil,” Dr Rao said. “The seeds can survive for up to six years in the soil. As many as 54 countries worldwide are infected by this weed.” Parthenium inhibits growth of other vegetation in its proximity by producing ‘allelochemicals’. It is highly allergenic to humans and also toxic to animals. Therefore, it is extremely essential to get rid of the weed, especially from agricultural land.
During the seminar at the ICRISAT headquarters on 27 August, Dr Rao listed several approaches to tackling the menace:
- Prevent spread of the Parthenium seeds by maintaining strict hygiene in fields
- If seeds are present in the soil, deep plough to bury them under 7 cm or more of soil and keep them buried for 6 years – till they lose their viability
- Destroy seedlings manually before flowering
- Growing competing plants like Cassia spp around Parthenium
- Herbicide spraying before seeds are set. Repeated spraying may be required.
- Glyphosate seems to be the most effective herbicide when used at the appropriate time, e.g. at onset of monsoon, when seeds germinate and seedlings emerge. However, adequate care – including use of protective clothing and gear – should be taken while using this herbicide.
- Biocontrol agents such as the Zygogramma bicolorata leaf-feeding beetle..
Considering the aggressively proliferating nature of the weed, Dr Rao suggested that a concerted effort – integrated weed management – employing all or most of the above strategies were needed for eradication of the plant