CONGRESS GRASS
or Chatakchandni,
(Parthenium hysterophorus in Botany):
A Menace
The invasive capacity and alleolopathic properties nearly permit it to disrupt the natural ecosystems.
Very sparse or sometimes no other vegetation can be seen in P. hysterophorus-dominated areas. These weeds rapidly invade new surroundings, often replace the indigenous species, and pose a serious threat to biodiversity in India. It is a dangerous invasive alien species (IAS). It exhibits the ability to invade and adapt to new habitats.
Recently many innovative uses of this hitherto notorious plant have been discovered. It confers many health benefits, viz remedy for skin inflammation, rheumatic pain, diarrhoea, urinary tract infections, dysentery, malaria and neuralgia. Its prospect as nano-medicine is being carried out with some preliminary success so far. Removal of heavy metals and dye from the environment, eradication of aquatic weeds, use as substrate for commercial enzyme production, additives in cattle manure for biogas production, as biopesticide, as green manure and compost are to name a few of some other potentials.
It is a flowering plant of family Asteraceae. It is native to the American tropics.
Its common names include Santa-Maria, Whitetop weed, Congress weed. In India, it is locally known as Carrot grass, Congress grass, Gajar Ghaas, Chatakchandni.
It is a common plant in India, Australia, and parts of Africa causing loss of agricultural yield. In some areas, heavy outbreaks affect livestock and crop production, and human health. It first appeared as a contaminant in imported wheat.
It starts appearing in spring in the end of February, and continues to appear till the onset of winter. In winter it remains dormant by forming rosette appearance. Congress grass attains a meter height at fully flowered stage. The weed bears numerous small white flowers aggregated together to form the Capitulum inflorescence. The seeds are fluffy, very small in size and light in weight easily dispersed by wind, water or through various human activities.
The plant produces Allelopathic chemicals that suppress crop and pasture plants, and allergens that affect humans and livestock. It also frequently causes pollen allergies. The common allergens found in congress grass are parthenin, coronopilin, tetraneuris and ambrosin.
As weed of agricultural crops, congress grass has marked effect on growth and colonization of Rhizobia (nitrogen fixing bacteria) in pulse crops.
Toxicity: Parthenin is a major toxic chemical, which is very toxic. Contact causes dermatitis and respiratory malfunction in humans, and dermatitis in cattle and domestic animals. It also is responsible for bitter milk disease in livestock, when fodder is polluted. Its pollen grains inhibits affects fruit set in tomato, brinjal, etc.
Control: Light infestations of Parthenium hysterophorus in cultivated fields may be weeded by hand. As reported, Paraquat sprays may be applied while the weeds are young. Most herbicides like Atrazine, 2, 4-Dichlorophenoxyacetic acid, Dalpan, etc are found partially effective against the weed. The plants Cassia sericea, Cassia uniflora, Cassia tora, Cassia auriculata, Amaranthus sinosus, Hyptis suaveolens, and Tephrosia purpurea have been found to replace the weed. Hence they can be used as replacement species to eliminate the weed.
The promising means of control are biological. A beetle native to Mexico, Zygogramma bicolorata, was first introduced to India in 1984. It defoliates and often kills the weed, and its damage to the young flowering tops reduces seed production.
Other means are being evaluated, e.g. a stem boring weevil Listronotus setosipennis, and a seed weevil Smicronyxlutulentus. Also rust fungi have been of some use: the winter rust Puccinia abrupt var. partheniicola plus the summer rust Puccinia xanthii.
Congress grass is a great health hazard to human beings and livestock population.
The pollen grains of the weed are allergic causing bronchitis, asthma, rhinitis, conjunctivitis, hay fever, sinusitis, common-cold, pain in neck and even depression in human beings. Frequent contact with the weed causes dermatitis, eczema, and gangrene. This weed is harmful and even fatal to the livestock population grazing in congress grass infested area. These animals suffer from itching, fall of body hairs, discolouration of skins, inflamed udder etc.
Is it known as Congress Grass due to white caps like inflorescence; or because of its monopolistic tendencies (as it enjoys monopoly in its growing habitat due to allelopathic property)? Please make your own choice of the reason.
Please note: I convey thanks to many authors, Wikipedia, etc for compiling this piece for common man so that they can do some work for living in a safer world.
The picture shows that it can grow anywhere, even on the divider on the busy road, with practically no one to offer manure, water, etc to the plant.
Pawan kumar Gupta
