Ever thought a puny weed could harm you ? If not now would be the right time to know that
some people have made it all safe for you. Born on August 4, 1937 to a farmer`s family
from Madapur in the Chamaraajanagar district of Karnataka, Dr M Mahadevappa is known as
much for his pioneering research in paddy varieties and hybrids as for controlling the
dreaded Partheniumweed internationally accepted as being hazardous to both men and
livestock Among its many harmful effects are dermatitis and respiratory diseases. Almost
every part of the plant except the root, is reactive.
The wasteland weed parthenium, also called congress weed and star weed,
has been growing naturally for centuries in Mexico, Cuba, North and South America, the
West- indies, Australia, Taiwan, Southern China, the Pacific Island, east and south Africa
and Canada.until about 1977,parthenium did not find any mention in the world`s worst weeds
list. But within the last decade or so, it has jumped to becoming one of the seven most
dreaded weeds anywhere in the world. It was noticed in India only from the mid-50sand is
presumed to have been accidentally introduced in Maharashtra. It was
first observed in Pune as a stray plant growing on rubbish heaps near the Agriculture
Collage by prof HP Paranjape, a retired horticulturist. However, since then, it has spread
out over the country, covering wastelands, railway yards, marshy patches, unused
cultivable land, grasslands, and roadsides in abnormal densities. It is in the light of
these statistics that Mahadevappa`s work assumes monumental importance.
Given his moorings, an intrest in the agriculture science came naturally to Mahadevappa .
He completed his bachelors, Masters and doctoral degrees in the 1960s. While he had always
known that parthenium was harmful to both humans and livestock, his intrest and curiosity
were aroused during one of his regular visits to the Dharwad. That was sometime in 1982-83
staying at a friend`s housenear the railway station,he noticed small circles of other
plants growing around the Parthenium weed. The follwing year, the Parthenium died while
the other plants multiplied. The pattern repeated the next year. It struck him that the
other plant variety, a species of Cassia, was able to exert what is known in botanical
terms as an allelopathic impact. It hindered seed germination and suppressed the growth of
the Parthenium. The weed does not die easily but remains dormant for as much as two to
three years. It waits for the right amount of moisture to germinate.
The seeds of a ground breaking study were sown. The plant was taken for examination to the
University of Agricultural Sciences, Bangalore. The particular Cassia species. A research
project was proposed and approved by the university, which put together a team to study
different aspects of Parthenium control and eradication. Dr Mahadevappa studied the leaf,
seed and other plant part extracts of Cassia sericea and concluded that these produced
certain parthenium-suppressing chemicals. Cassia seeds were collected from Dharwad and
planted in the Parthenium-infested areas of Bangalorewith amazing results.in two to
three years, the growth of Parthenium was controlled considerably. The search surged
The doctor`s curiosity gave way to determination; to evolve an integrated approach with
which to remove Parhenium from the face of Karnataka and other adjoining states. A few
more plants which had similar effects on Parthenium were also listed. Studies by other
agricultural scientists were thoroughly examined and species of Australian beetles, were
scrutinised In 1985, Dr Mahadevappa made his studieson the control of Parthenium public.
These clearly demonstrated that only a cooperative approach, now called the Integrated
Parthenium Weed .Management (IPWM), would stem the impertinent weed. Since Parthenium had
been a native of latin American countries, botanical enemies and insects had
always accompanied its growth. But in India, it was comparatively new. Its growth became
relentless due to the absence of natural restrictive agents. Contrary to earlier studies,
it was observed that botanical agents were different for different areas.
But what strategy exactly does IPWM, the result of nearly two decades of intensive
research, lay out. The maintenance of natural bio-diversity. In layman`s language, that
would mean not disturbing existing flora. In place where cleaning and exposing the soil is
unavoidable, Cassia Sericea or other proven botanical agents like Tephrosia Purpurea,
Stylosanthes Scabra and other can be grown. The project also involves watching out for
rain and build up of mexican beetless (Zygogramma). When they become readily available in
large numbers, they are to be released in infested areas. Where none of this is possible,
manual removal has to be taken up. But farmers have to be extremely careful and not get
affected. Chemicals are spread only as a last resort.
Several papers by Dr. Mahadevappa on the weed have also been publised worldwide. The
doctor was invited in the late 80s to showcase his work at the Weeds Conference in
Malaysia. He subsequently went to USA and Kenya in 1992 and 1993 respectively. his rather
illustrious career has also seen a number of national and international awards. Having
served as vice chancellor at the University of Agriculture Sciences, Dharwad, he is now
doing a term as chairman of the Agriculture Scientists Recruitment Board. To him also so
goes the credit of having organised the First International Conference on Parthenium
Management in October 1997.
His hard work has paid off. IPWM has controlled the growth of
Parthenium by nearly 70 to 80 percent in Karnataka. In southern Maharashtra, growth levels
have come down by close to 60 to 65 percent. Bangalore is almost free of the menace. The
weed, however, cannot be tackled alone. it needs a societal effort, says the
good doctor. His recommendation: Municipal authorities in each state and city must sit
down and chalk out extensive joint strategies.