A recent survey conducted by the author and co-workers on the prevalence of parthenium in
the northern parts of Kamataka viz., Belgaum, Dharwad, Haveri, Gadag, Raichur,
Gulbarga, Bijapur, Bidar, Bellary, Koppal districts revealed that considering its growth
in the early 80s as benchmark, the weed has been reduced to more than 60 per cent
both in the agricultural and waste lands. Agents responsible for this control are mostly
botanical species with some significant effect here and there of the beetle Z. bicolorata
in rainy season. Predominant botanical agents responsible in the order of importance
are: C. sericea, C. tora, H. suaveolens and Amaranthus spinosus. In the district of
Bijapur in the rocky area, however, T. purpuria has played a major role. In Uttara
Kannada district and also adjoining hilly regions of Belgaum and Shimoga districts, Cassia
occidentalis and Croton sparciflorus have played a major role. The two species viz.,
C.tora and C.occidentalis have restricting the parthenium in hilly and semi hilly
regions even from the initial stages of parthenium entry into the state. Coming to the
southern parts of Karnataka, in the dry regions of the districts of Chitradurga and
Chikkamagalur, Tephrosia purpuria and C. occidentalis have played a major role in
preventing the spread of parthenium. It may not be out of place to mention here that
fresh growth of parthenium weed is seen in newly opened up forests in the
transitional areas
and more so towards plains indicating that the weed finds it difficult to establish in the
hilly region but it easily establishes in the plains. Also in the plantations of mango,
sapota, coconut and such other perennials, the weed puts up luxurious growth if frequent
ploughing intercultivation and weeding is not attended to.
In Bangalore city, vacant sites in many residential areas where botanical agents like C.
sericea, M.jalapa and A. spinosus were planted during early 90s are now free from
parthenium infestation to the extent of 90 per cent. On roadsides where, seeds of
botanical agents were sown during early 90s C. sericea replaced parthenium very fast but
in the process of widening of Bangalore-Hosur road, the treated area is all covered
under road and nothing can be seen now. However, near Titan watch Co., and Leyland
factories near Hosur, replacement of parthenium by C. Sericea is quite visible. Frequent
disturbance in annual road cleaning activity has deterred the growth of C. sericea and
other botanical agents. The public and highway authorities need to be educc-Led on the
role of naturally existing or deliberately planted botanical agents in controlling the
invasion and subsequent growth of parthenium. On Mysore road in Bangalore city on either
side, A. spinosus and Hyptis suaveolens have totally taken over by suppressing parthenium
weed. On the old Madras road in the outskirts of Bangalore city viz., on either side of
the
railway track (near over bridge), replacement of parthenium by C.sericea is distinctly
visible. Next to this on the tank bund to the west of high way towards Hosakote, Hyptis
has replaced parthenium to the extent of 90 per cent.
In Mysore city in Kuvempunagar and Nanjangud road, C. sericea has replaced parthenium in
short stretches wherever C. sericea was sown during 1994-95. In Chamarajnagar district
along the state highway between Nanjanagud and Chamarajnagar towns, vast stretches
of parthenium infested road sides are replaced by C.sericea particularly near
Mahadevapura and Bendaravadi villages. In Chamarajnagar town, C.sericea has
replacedparthenium in areas adjacent to Court, First grade college and Department of
Sericulture. Near Srirangapatna along both sides of highway, T. purpuria has resisted
entry of parthenium.
Due to efforts of voluntary organizations, sowing of C. sericea seeds has started
replacing parthenium very fast in Davanagere city and peripheral areas. In Shimoga
district also replacement of parthenium by C.sericea is quite visible on the Harihar road
and vacant lands in the city.
In Sangli, Kolhapur and Solhapur districts Maharashtra state, Cassia, species
(sericea and to some extent tora) have replaced parthenium to more than 60 per cent.
In Tamil Nadu, through the efforts of one Captain Kasirajan ofVirudhanagar in Madurai
district, a stretch to the extent of more than one km on the Madurai - Kanyakumari highway
and some parts within Virudhanagar town, parthenium is replaced by C. sericea.
In Andhra Pradesh on the Hyderabad road near Pattancheru, some seeds of C. sericea
sprinkled during 1994-95 have grown and have started displacing parthenium and the
C.sericea colonies are enlarging year by year as observed by the author between ICRISAT
and Hyderabad city during 1999.
Effect of the beetle
The beetle, Z. bicolorata which was released in mid eighties has spread on its own from
single release at Bangalore and also through separate releases in other parts of the
country has spread in many places in Kamataka, Tamil Nadu, Andhra Pradesh and Maharashtra.
The beetle has been defoliating the parthenium plant
during the rainy season. Total defoliation leaving only stem is seen in the months
of August, September and October in Kamataka and Maharashtra and during October and
November in Tamil Nadu. Suppression of parthenium during the rainy season is very
impressive and the release of Z.bicolorata can serve as an
important component of the Integrated Parthenium Weed Management Technology.
Recent report from the ICAR committee revealed that the beetle can not become a pest
on crops like sunflower and niger, clears the way for including this as a component of
IPWM.
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