Parthenium became a menace due to wide ecological amplitude, profuse growth, fast multiplication, rapid spread, agricultural and health hazards. Several methods have been recommended to suppress its growth.
But no method appears to have worked satisfactorily as each method suffers from one or more limitations such as inefficiency, prohibitive cost, impracticability, polluting the environment and only temporary relief etc. The integrated parthenium management approach recommended recently seems to be promising.
To feed the ever-increasing population of our country, we are trying to enhance agricultural production. In this respect several promising technologies are coming in the way i.e. good quality seed , drip irrigation, SRI technique and others.
In this background, parthenium infestation reduces yield 30 to 40 percent; means it is pulling back our efforts for agricultural acceleration. Already the weed has occupied over 5 million ha of land in the country. Therefore, the time has come to consider parthenium invasion as a forthcoming danger in agriculture, considering its negative impact on agriculture.
Our unawareness about this weed for a long period has given it to its’ full potential spread. Parthenium is a genus of North American shrubs in the sunflower tribe within the daisy family.
It is a common invasive species in India, Australia and parts of Africa.
Parthenium hysterophorus invades all disturbed land, including farms, pastures and roadsides. In some areas, outbreaks have been of almost epidemic proportions, affecting crop production, livestock and human health. Therefore, integrated approach for parthenium management is need of the hour.
Need of parthenium management
- It reduces yield, 30 to 40 percent
- It is a vigorous species, which colonizes in grassy land. It grows rapidly in bare areas along roadsides and water points.
- It is a major health hazard to human beings.
- It reduces the production of pasture.
- Its pollens are a major cause of asthma, especially in children and elderly people.
- It emits carbon dioxide and hence, poses a problem to nitrogen fixation and becomes a parasite, dependent on standing crops and animals in its vicinity.
- It is a major cause of allergic, Trinities sinusitis, affecting about 10 percent of the people who live near it.
- It causes irritation to eyes.
- It is a major cause of dermatitis, a skin disease, among animals and human being.
- It reduces yield of milk and weight of animals.
Parthenium offers a big challenge
Parthenium offers a big challenge to all attempts of control because of its high regeneration capacity, production of huge amount of seeds, high seed germinability and extreme adaptability to a wide range of ecosystem.
Parthenium has been declared noxious in America, Australia, India and many other countries especially those having tropical climate. Scientists describe it as a “poisonous, allergic and aggressive weed posing a serious threat to human beings and livestock.” It squeezes grasslands and pastures, reducing the fodder supply.
The presence of parthenium in cropped lands results in yield reduction upto 40 percent. It is also responsible for bitter milk disease in livestock fed on grass mixed with parthenium.
It is a biological pollutant and highly successful in distribution. The reasons for its fast spread are:
- High germination ability throughout the year
- Large seed production ability
- High survival rate: - Seeds do not have a dormancy period and are capable of germinating anytime when moisture is available. The highest germination rates are at the temperatures ranging from 120C to 270C. Persistence tests demonstrated that more than 70 percent of parthenium seeds buried at 5 cm below the soil surface survived for at least 2 years, whereas seeds on the soil surface did not survive for longer than 6 months. Seed viability for 20 years has also been reported.
- Extreme adaptability in a wide range of habitats.
- Easy dispersal of seeds, due to its high fecundity. A single plant can produce 10000 to15000 viable seeds and these seeds can disperse and germinate to cover large areas. A large single plant produces upto 100000 seeds in its life cycle. More than 340 million seeds per ha can be present in the surface soil.
Mechanical and cultural control of Parthenium
- Manual uprooting of parthenium before flowering and seed setting is the most effective method. This is easily done when the soil is wet.
- Ploughing the weed in before the plants reach the flowering stage and establishing pastures or other plants may be effective.
- Competitive replacement of parthenium can be achieved by planting species which will compete with the weed and reduce its population. (Species are-Cassia sericea, Cassia uniflora, Croton bonplandianus, Croton sparsiflorus, Amaranthus spinosus, Sida acuta, Tephrosia purpurea, Stylosanthes scabra, Cassia auriculata and Cassia tora).
- Planting Cassia species (a non-nitrogen fixing leguminous herb) colonizes more aggressively without giving scope for parthenium to manifest.
- Crop rotation using marigold (Tagetes spp.) during rainy season instead of the usual crop, is found effective in reducing parthenium infestation in cultivated areas.
- There is a high risk of spreading parthenium by the movement of vehicles, livestock and crop produce. Washing down vehicles/machinery before entering into a non-infested region will restrict the spread of seeds.
- Movement of cattle during rainy season will aid in the spreading of seeds in muddy soil. If this is unavoidable, it would be safe to hold cattle in yards or small paddocks to let seeds drop from their bodies and tails before releasing them into larger areas.
- Also, while purchasing cattle feed and crop seeds these need to be checked for contamination by parthenium seeds.
- Fire has been used to control the first flush of emergent weeds at the beginning of the rains, but is only considered to be a short term control measure.
- Physical methods like uprooting, tillage, mowing, flame throwing, burning, hand weeding, etc. are effective in small areas, isolated pockets and agricultural field.
- Growing of competitive crops like maize, sorghum and sunflower to suppress parthenium.
- Making compost –when the weed reaches 50 percent of seed setting during flowering.
- Mulching has smothering effect on weeds by restricting the photosynthesis.
Biological control of Parthenium
The leaf feeding beetle, a beetle native to Mexico (Zygogramma bicolorata) is capable of defoliating and killing this weed and the stem galling moth (Epiblema strenuana) are widely used in several countries to manage parthenium. The moth significantly reduces flower and seed production of the weed, especially at young age.
Other major bio-control agents used are Stem boring weevil (Listronotus setosipennis),Seed feeding weevil ( Semicronyx lutulentus), Leaf mining moth (Bucculatrix parthenica), Stem boring moth (Platphalonidia mystica) , Stem galling weevil (Conotrachelus albocinereus), Root boring moth (Carmenta ithacae).
Use of rust fungus (Puccinia abrupta partheniicola). Uredospore suspensions from 3-week old pustules of the rust have been applied to the foliage of parthenium and a consistent control effect has been achieved.
Pathogens like Fusarium pallidoroseum, Puccinia melampodii, Sclerotium rolfsii and Oidium parthenii also show good potential as bio-control agents. Extract of different plant parts and whole plant of Cassia tora caused reduction in germination of parthenium.
Chemical control of Parthenium
- Use of Glyphosate, Atrazine, Metribuzin, Dicamba, 2,4-D, Picloram has been promising.
- The plants should be treated before flowering and seed setting and when other plants, especially grass are actively growing and can recolonize the infested area.
- In open wasteland, non cropped areas and along railway tracks and roadsides, the spraying of a solution of common salt (Sodium Chloride) at 15-20% concentration has been found effective.
- Paraquat (Gramxone) solution is sometimes applied to plants, when the weeds are young.
- In Australia, spot spraying with Atrazine plus a non-ionic surfactant is recommended as a pre-emergence treatment.
- Post emergence control has been achieved with 2,4-D, often in combination with Picloram.
- Some of the herbicides, such as Imazapyr, Oxadiazon, Oxyfluorfen, Pendimethalin and Thiobencarb have also been reported to be highly effective against parthenium weed.
- Bromoxynil+MCPA were the most effective of a range of post-emergence treatments.
- Glyphosate, Glufosinate, Chlorimuron and Trifloxysulfuron applied at the rosette stage provided greater than 93% control.
- Halosulfuron, MSMA, Bromoxynil, 2,4-D and Flumioxazin gave 58-90% control.
- Norflurazon and Clomazone were also highly effective.
- Atrazine @ 1.25 kg/ha prevented weed emergence completely upto 150 DAS followed by Terbutryne@ 6.0 kg/ha and RH 8817 @2.8kg/ha.
- Post emergence herbicides viz. Diquat @ 0.5 kg/ha, Dicamba @ 2.05 kg/ha, Picloram@ 1.61 kg/ha, 2,4-D (Amine) @ 5.4 kg/ha, Glyphosate @ 0.9 kg/ha. ; Chlorimuron Ethyl @ 20 g/ha, Metsulfuron @ 3.5 g/ha. Glufosinate @ 1% were effective in non-cropped areas.
- Bentazon @ 1.5 kg/ha at 25 DAS in soybean effectively controlled parthenium.
Integrated Management of Parthenium
The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are the following:-
- The best method of invasive species management is prevention. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing.
- Controlling the weed before it seeds will reduce future problems.
- Control is generally best applied to the least infested areas before dense infestations are tackled.
- Consistent follow-up work is required for sustainable management.
- To control this weed, it is recommended to pull out the plants before they flower, making sure to remove all of the root system to avoid regrowth from root leftovers.
- A number of herbicides (foliar applications) registered for use against this weed, when using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.
- The best method of control is to maximize competition against the weed by good grass growth, which requires exclusion of grazing livestock until grass has become re-established, followed by reduction in stocking rates to prevent reinvasion by the weed.
- Ploughing before flower set and burning when the plants are dry and mature
- Application of atrazine or other herbicides like 2,4-D, Paraquat, Glyphosate, Diuron, Dalapon
- Using Cassia sericea to displace parthenium weed
- biocontrol using Zygogramma bicolorata.
The govt. may enact legislation for removal of parthenium in public places. There is a need for community efforts in manual removal of weed before it starts flowering. Limited use of recommended weedicides can be adopted in suitable areas.
The role of plant species in competitive displacement of parthenium has to be further evaluated. Particularly the plant species should have some economic value and should not pose health/environmental problems. Maximum efforts should be directed towards importation of host specific insects.
Department of Agricultural Extension,
College of Agriculture, Bidhan Chandra Krishi Viswavidyalaya,
Agricultural Farm-713101; Burdwan, West Bengal,