PARTHENIUM HYSTEROPHORUS is widely growing weed found in abundance everywhere in irrigated and non-irrigated areas of the Punjab. As one knows that the weeds are the plants that are competitive, persistent, pernicious, and interfere negatively with human activity. Weeds have major economic, environmental and social impacts causing damage to natural landscapes, agricultural lands, waterways and coastal areas. Parthenium hysterophorus is an aggressive ubiquitous annual herbaceous weed with no economic importance unraveled till now. The aim of this article is to create awareness of the emerging problem to mankind and ecosystem and to develop measures for its control by adopting common strategy to reduce the threat of this noxious weed in Pakistan.
Parthenium hysterophorus is amongst ten of rapidly growing and noxious weeds of the world, locally called as Gajar Booti which is emerging as a severe threat to the agriculture of Pakistan particularly to Punjab. It is worldwide known as altamisa, carrot grass, bitter weed, star weed, white top, wild feverfew, the “Scourge of India” and congress grass. It is enormously detrimental to heath of flora and fauna. It may reduce productivity of crops thus a serious threat to food security in long run.
Technical name of this weed is Parthenium hysterophorus L. Its threat was identified during the last decade of previous century. Origin of this noxious weed is Mexico (Central America) from where it rapidly disseminated to Australia, Africa and Asia. In 1956, it was identified in India since then it is spreading other parts of sub-continent. It is reported to be heavily infested in China, Taiwan, Vietnam, Ethiopia, Kenya and South Africa where it has become an emerging threat to agriculture.
It is gifted to Pakistan by India as it poses through the river water resultantly; its population is increasing at drastic rate in Pakistan. In Pakistan, initially it appeared on coarse areas of residential colonies, railway tracks, roads, drainage and on the banks of irrigation canals. The survey of the Agriculture Department of Punjab reveals that Parthenium hysterophorus is rapidly shifting to cultivated areas thus posing severe threat to the production of crops. Now during summer, it can widely be seen abundantly in rice, maize and sugarcane crops. Its infestation is also seen not only to Punjab but also in KPK and some parts of AJK.
It is annual herbaceous weed having leaves light green in color covered by delicate small hair but with aging of plant density of hair reduce on leaves. Lobes are present on the edges of the leaves. It is deep rooted plant having erect and stiff stem, by the maturity of plant stiffness is reduced. Plant height is up to 2 meters. It completes its life cycle and produces seeds in four weeks in favorable environmental conditions. Its flowers are of white color having shape like star which turns to brown or black color at maturity of seed. Every flower has the capability to produce 4-5 seeds with 2mm length. Plant has the capability to produce ample quantity of seeds and is viable for long period. The seeds disseminate through wind to large areas. One plant can produce 25000 seeds and can remain viable for seven years. The rainy season is considered to be favorable for growth, development and inflorescence of this weed.
It has tendency to flourish in all type of soils but clayey fertile soils are most suitable. Seeds usually mature from March to April. Areas under relatively high rainfall favor its germination and growth because seeds require enough moisture for its germination due to the very reason its germination and growth is found to be restricted under low rainfall areas. Optimum temperature ranges from 12- 27 0C for its germination. Seed starts germination in 4-7 days under favorable environmental conditions.
This weed has been reported causing many health hazards with epidemic proportions. This weed is considered to be one of the causes of respiratory allergic problems, contact dermatitis, mutagenicity in human and livestock. Persons exposed to this plant for a prolonged period be manifested the symptoms of skin inflammation, eczema, asthma, allergic rhinitis, hay fever, black spots, burning and blisters around eyes. It can also cause diarrhea, severe popular erythematous eruptions, breathlessness and choking. The pollens of P. hysterophorus can cause allergic bronchitis to those who are exposed to it.
Owing to allelopathic characteristics of this weed, crop production can be drastically reduced. As the weed not only competes for nutrients, water, space and light with crop plants but also release growth inhibiters to neighboring flora. Moreover, it is also providing shelter to many pests of crops as well as produces carbon dioxide which can intervene nitrogen fixation by Azotobacter and Nitrosomonas present adjunct to plants thus, has detrimental effect on the fertility of soil.
It is a prolific weed plant produces many seeds henceforth; a single plant has competent to produce up to 25000 seeds. Wind, water, animals and agricultural implements are the main source for their spread to all around the ecosystem.
In the light of above comprehensive description regarding P hysterophorus, it is most concern to all stakeholders of agriculture as the pressure is mounting at rapid pace with alarming threats. Therefore, it is suggested to adopt following preventive measures for the minimal effects of the threats including uprooting of this noxious weed before flowering on small areas, on large scale integrated management strategies must be adopted, awareness campaigns must be undertaken to make this noxious weed aware among farming communities, regarding chemical control glyphosate @1 liter/acre must be applied for prompt control.
Under the above scenario, the duties of extension services have been considerably enhanced to create awareness regarding the issue through its infrastructure and print/electronic media. If it is done, it would be a great service to humanity and the country.