Introduction
Parthenium hysterophorus L., commonly called as carrot weed, white top
or congress grass in India is a herbacious erect and annual plant belonging to family
Asteracae (Compositae). The origin of parthenium is considered to be Mexico, America,
Trinidad and Argentina. Within last 100 years, it has found its way to Africa, Australia
and Asia. In Australia and India parthenium has achieved the status of "worst
weed". Its surmised that parthenium possibly got entry from USA through the imported
food grains (Vertak, 1968)
or through the cereals got for experimental purpose (Lonkaref al.,
1974). In most of the publications, first occurrence of parthenium in India has believed
to be in 1956 when it was first noticed by a retired horticulturist Prof. Paranjape and
described by Rao (1956). However, some reports trace its history of occurrence about one
and half century older than as reported by Rao (Roxburgh, 1914, Bennet et al., 1978 and
Maiti, 1983). Its presence in India before 1956 gets further confirmation from a herbarium
record collected by Dr. Brandis in 1880 in Forest Research Institute, Dehradun.
Tom these records, it is clear that parthenium has entered India before
1910 and lived unknown till 1956. It is clear that since 1956, parthenium has spread like
wild fire throughout India and has achieved the status of "worst weed".
According to Mahadevappa (1996), parthenium status, in terms of its seriousness in
different states of India is Uttar Pradesh, Karnataka, Maharashtra, Tamil Nadu, Andhra
Pradesh, West
Bengal, Madhya Pradesh, Gujarat, Orissa and Bihar, in that order of
magnitude, contrary to earlier observations when it was catagorised as serious weed of
Maharashtra, Karnataka, Andhra Pradesh and Delhi (Krishnamurthy et al., 1976). The
parthenium intensity has been estimated less in high elevation. It is estimated that about
5 million ha area has been invaded by parthenium in India.
Parthenium is a poisonous, pernicious, problematic, allergic and
aggressive weed posing a serious threat to human beings and livestock. This weed has been
considered as one of the greatest source of dermatitis, asthama, nasal-dermal and
naso-bronchial types of diseases. Besides these ill effects, it also causes several other
problems like blockage of common pathways and orchards and reduces the aesthetic values of
parks, gardens and residential colonies. Mostly parthenium is a weed of fallow and waste
land but its impact on agricultural crops has not been well documented. Its infestation
has been noticed more in rainfed than in irrigated agriculture. /
Present scenario of parthenium management
Ever since the weed became a menace in India and other countries,
efforts are being made to manage the weed by different methods. But so far, no single
method has been proved satisfactory, as each method suffers from one or more limitations
such as high cost, impracticability, environmental safety, temporary relief etc. A brief
of various management practices being employed against parthenium is given below to take
an insight of merits and demerits of the method before switching over to future strategy
for effective parthenium management.
Manual and mechanical methods
Manual methods are very expensive and can not be employed everywhere.
It is feasible only in high value crop. The relief from this method is temporary and needs
to be repeated. Mechanical removal with the help of tractor, plough, etc., is possible
upto certain extent and only in open fields.
Legal .methods
The management of parthenium was also tried in India through the legal
act, first in Karnataka state. Government of Karnataka, issued a notification on 23rd
Oct., 1975, declaring parthenium a noxious weed in terms of section 3 read with sub
section seven of the section two of the Karnataka Agricultural Pests and Disease Act,
1968. Under this act, to remove parthenium, notices were issued in Bangalore once or twice
during the eighties by Municipal Corporation but were not followed up. Thus, inspite of
this comprehensive act, it was a total failure to get the weed removed from. Bangalore or
elsewhere.
Biological methods
During last few years much emphasis has been laid to control parthenium
through various biological agents like insects, pathogens and plants.
*By Plants
In recent past, this approach gained momentum after reports that Cassia
sericea (C. uniflora) can be used to control parthenium (Singh, 1983 and Mahadevappa and
Ramaiah, 1988). Cassia sericea, a non nitrogen fixing leguminous plant was suggested to be
used by adopting two approaches namely maintaining of naturally occurring biodiversity and
planting of specis in target area (Mahadevappa, 1996). In this approach, two apprehensions
were observed by Balyan et al., (1997) (a) In planting of C. sericea in areas of
parthenium dominance, in the beginning, parthenium has to be removed physically and
mechanically and there are limitations of uprooting parthenium in undulating areas (b) to
remove one weed (carrot weed), another weed (Cassia) has to grow, which may also pose
danger to field crops and orchards in coming years. .In Jabalpur (M.P., India),
suppression of parthenium by marigold showed encouraging results and this practice was
also advocated for parthenium suppression (Kauraw and Bhan ,1995b).
*By indigenous insects
In India, many insects have been reported on parthenium but none of the
indigenous insect was found to be host specific. The occurrence and role of indigenous
insects have been reviewed and discussed by Sushilkumar and Bhan (1995). A cerembycid
borer Oberea sp. has been found infesting parthenium upto 29.9 per cent in Jabalpur and
Vindhya nagar (M.P.) (Sushilkumar and Bhan, 1997).
*By exotic insects
Owing to lack of effective indigenous insects, three insect species
have been imported in India so far. Among these only the chrysomelid beetle Zygogramma
bicolorata imoorted from Mexico could be established and successfully controlled the
parthenium Bangalore, when released after host specificity test (Jayanth, 1987). But this
beetle was involved in a controversy after reports that it feeds on sunflower and
xanthium. This aspect has been reviewed and discussed in detail by Sushilkumar and Bhan
(1995). Balyan et. al., (1997) suspected the usefulness of biocontrol agents due to
variable climatic conditions in India and difficulty in multiplying and producing huge
quantity of bio-agents under laboratory conditions besides restriction of their host
specificity.
*By pathogens
Some pathogens have been reported to attack parthenium (Luke, 1976 and
Kalidas, 1981). During survey from 1992-94 in an around Jabalpur, many fungal species were
isolated infesting leaves, seeds and stem/roots of parthenium. Among these use of Fusarium
pallidoroseum and Sclerotium rolfsii against parthenium is also very common in India
(Padmanabhan, 1982 and Kauraw and Bhan, 1995a).
Chemical methods
Researches on chemical control of parthenium in India gained momentum
since eighties. Bromacil, diuron, terbacil @ 1.5 kg per ha were found effective as
herbicides (Kanchan and Jayachandra, 1977). Diquat 0.5 kg per ha in 500 I spray
effectively controlled parthenium at all growth stages (Dhanraj and Mitra, 1976). Spraying
of 2 kg 2,4-D sodium salt or 2 I MCPA in 400 I of water controlled the growth of
parthenium seedlings. Likewise, MSMA @ 4 I in 4001 of water was able to control fully
grown parthenium (Mahadevappa,1996). On the basis of two years research Balyan et al.,
(1997), gave concrete recommendations for control of parthenium (Table 1). They also
advocated the supremacy of chemical control over other control measures on the ground of
quick relief, time saving and cost effectiveness.
Future strategies for effective parthenium management
Present methods of parthenium control discussed above indicate that there are some merits
and demerits in each methods. It is also clear that any single approach is not enough to
manage parthenium, hence there is an urgent need to adopt an integrated parthenium
management approach by amalgamating more than one options. On the basis of demerits of the
above methods, an attempt has been made to give some suggestions to improve the existing
methods for evolving effective strategies against parthenium. Physical and mechanical
management It has been seen that cuttings of parthenium enhance their regeneration. So if
mechanical or manual methods are to be adopted, weed should be uprooted and such
operations should be started before blooming as uprooting after flowering will be sheer
wastage of time and money. As manual removal is not cost effective it can be advocated
only in limited situations. If it becomes imperative to use labour, persons engaged for
the job should be ascertained for their parthenium sensitiveness.
Cultural management
Some researchers have advocated growing competitive crops to suppress
parthenium but as parthenium is mainly a waste land weed, the scope of this practice is
limited to only certain situations.
Legal management
In India, Laws and Acts to suppress weeds exist but their proper
implementation have never occurred and Acts remained in files only. If such an act is
passed, administration of the state in collaboration with the scientist should give a wide
publicity through TV, video, radio, posters, seminars, etc., to bring awareness and
educate the people for the implementation of the Act. On the lines of Karnataka
Government, other states where this weed has assumed alarming situation should also enact
Acts against parthenium with more administrative control.
Biological management
Past efforts through biological control.agents indicate that parthenium
management through biocontrol agents can not be as simple as in some other successful
cases because of high regeneration capacity, large seed production ability, germination
ability throughout the year and extreme adaptability of parthenium in wide range of
ecosystem. Some future strategy in biological management may be as follows :
*Even if Mexican beetle Zygogramma bicolorata gets clearance from the
blame of its feeding on sunflower, it is not sufficient to manage parthenium because this
beetle is able to make sufficient population build up only during July to September. On
the contrary, partfaenium is able to germinate throughout the year. Therefore, such
insects which are active during most part of the year will be more helpful to manage
parthenium. Search of these types of insects in the native home of the parthenium and
their introduction in our country will remain an essential component of future strategy,
* Fresh efforts are needed to look into the case of failure of past
efforts in establishing of seed feeding weevil Smicronyx lutulentus. The establishment of
this insect along with Z. bicolorata may be helpful to manage parthenium more effectively.
*More concerted efforts are needed to investigate the role of
indigenous insect fauna.
* So far, only countable efforts have been made to search for pathogens
against parthenium (Kauraw and Bhan ,1995a). More concerted research in this direction is
imperative in the development of mycoherbicides for effective parthenium management. It
has been reported that integration of bioherbicide with reduced rate of chemical
herbicides can successfully improve the activity of mycoherbicides towards weed. It has
also been suggested that bioherbicide comprised of native pathogens may be more effective
than introduced pathogens because of more adaptability and no necessity of quarantine
measures (Quimby and Walker,1982). This approach can be explored to manage parthenium, as
earlier studies have already revealed a few effective pathogens.
*The role of marigold should get encouragement in residential colonies,
office premises and farm houses with the help of peoples' participation. Using marigold,
parthenium suppression can be achieved and aesthetic value will be maintained. The role of
marigold in waste land and along the roadside is not justifiable as marigold require
little more attention to avoid to be plucked on flowering from the greedy people who may
think to fetch little money by selling the flowers in the market and this attention can be
made only by colony and office premise people.
*The role of Cassia sericea and other competitive and haimless plants
have to be reinvestigated under a long term trial programme to see the actual damage, if
any by replacing weed as has been apprehended by some researcher. But it is a fact that in
comparison to parthenium, C. sericea or C. tora are very less harmful and can be managed
easily in case they reach at the alarming stage. To get high germination rates of Cassia
sp. while applying against parthenium, seeds can be soaked in concentrated sulfuric acid
for 12-21 min (Jayakumar et al., 1989).
Chemical management
The management of parthenium by herbicides has been considered only a
viable option by Balyan et al., (1977) but in our view this approach alone is not
justifiable as the effect of herbicide will always be of a temporary nature and repeated
operations are required which will not remain cost effective as parthenium is a weed of
waste land so and common man will never invest his money in this venture. Moreover, plants
suppressed by
chemicals have been observed to regenerate after remaining dormant for
a few days. Chemical treatment can only kill existing population at the given sites but
cannot prevent the entry of the seeds from neighbouring places. Because of continuous seed
production ability of parthenium throughout the year, reinvasion of the once controlled
area can hardly be checked unless the seed source itself is controlled. The recommendation
of common salt and soap water is also not justifiable as the application can spoil the
existing soil conditions and can deteriorate the environment. Nevertheless, only in very
limited situations, chemical use is justifiable for quick relief. Following research
strategies are needed for chemical parthenium management:
*Detailed study of herbicide action on the biology and ecology of
parthenium should be done before recommending any herbicide because of the fact that
parthenium is very hardy weed and may soon develop resistance against herbicides.
*As parthenium germinates throughout the year, application of pre and
postemergent herbicide in sequence may give effective conrol of parthenium. This approach
needs in-depth investigation.
*Development of newer group of herbicides with the attributes of
economically cheap, persistant but having less residual effects are imperative.
*Most sensitive stage of growth of parthenium should be identified for
effective management.
Management by utilization
The large scale utilization of parthenium will also be one of the
effective methods to manage the weed. Parthenium has been well documented for its
insecticidal, nematicidal and herbicidal properties (Gajendran and Gopalan 1982, Bala et
al., 1986 and Pandey et al., 1993) besides oxalic acid (Mane et al.., 1986) and biogas
production (Gunaseelan 1987). The search on more effective utilization of parthenium will
render it for effective management.
Integrated parthenium management
From the past researches, it is clear that parthenium can only be
managed effectively by adopting integrated approach involving many options in combination.
The role of exotic insect Z, bicolorata can be suspended in integrated approach till its
clearance from the blame of a potential feeder of sunflower. An integrated package of
practices for effective parthenium management can be adopted as follows:
* On the lines of Karnataka state, other states of India should enact
Acts for parthenium management, keeping in view the seriousness of the parthenium. Such
acts must be given high publicity through various media and follow up action by the
administration. Local leaders of urban and rural areas, volunteers, NGOs and village level
officers and assistants should be taken into confidance. Efforts should be made to give
them 1-2 days training about parthenium hazards and the benefits and about its control. If
this sort of strong group is made, it will further take care of the programme
implementation.
* During summer and winter, the population of parthenium remains low in
comparison to rainy season and therefore spraying of glyphosate will be of much use to
reduce the intensity of parthenium in forthcoming season. Before monsoon pre-emergent
herbicide like atrazine, metribuzin or bromacil @ 2, 2.3 and 1.5 kg per ha can be applied
in the sites already marked for dominant patches. Tills application will certainly reduce
the intensity of the seed bank. With the onset of monsoon, emerged seedlings of sufficient
height can be controlled by spraying of glyphosate @ I per cent solution. This application
should be made at any cost before blooming.
*During rainy season, soil remains wet and hence manual or mechanical
removal can be done before the onset of flowering, with the help of peoples participation.
*On the onset of monsoon, seeds of C. sericia or C. tora can be sown in
highly dominated areas by parthenium after seed treatments as suggested by Jayakumar et
al., (1989) to ensure good germination. Likewise, marigold seeds can be sown in the vacant
soils of residential colonies, farm house and office premises with the
onset of monsoon. After sufficient wetting of soil, seedlings can also be transplanted for
quick establisliment. The deliberate sowing of these plant species will be required only
for initial 1-2 years, later on, they will establish themselves. In nutshell, for
effective parthenium management in a given geographical area, serious efforts are
imperative. Deep consideration should be given about the site, nature of infestation (like
arable, non arable, waste land, scanty or adundant) and stage of the growth of weed.
Efforts to manage parthenium should not be
stopped only after one season but should be prolonged till the complete
seed bank is exhausted. Otherwise, all the efforts will go in vain due to high seed
production capacity of the weed. Further, adequate quarantine measures should be adopted
to check the emigration and emmigration of the weed. Therefore, combined efforts by
researchers, social workers and department of horticulture, agriculture and forestry are
required.
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