In recent decades environmental problems that hog the world’s attention relate mainly to pollution, ozone depletion, global warming and more. Yet few are aware of the insidious damage posed by biological hazards, one of which is the expansion of congress grass at an alarming and unprecedented pace. Congress grass scientifically known as Parthenium Hysterophorus, a native of West Indies and Tropical America, has established itself almost throughout India.
Spatial Dispersal of Congress Grass
Reportedly congress grass was first observed in Maharashtra from where it spread to other states and is now seen proliferating almost throughout India. By 1963 the weed had found an entry into the state of Jammu and Kashmir. By 1969 it completely naturalised the territory of Delhi. At present no part of the country is free from Parthenium Hysterophorous. It is primarily grouped as a weed of non-cropped areas, but it can also be seen dispersed in the cropped fields, particularly with the kharif crops in rainy season.
Means of Dispersal of Congress Grass
Seeds of this weed are easily dispersed by wind and water. Very small white flower of this plant contain seeds which can be lifted by the wind. Also, irrigation water carries away the seeds to fresh areas aiding its infestation.
Congress Grass Hazards
The weed is an environmental hazard and throws up dangerous implications for man, animal, air, water and agriculture. Broadly we can categorise its hazardous impacts under three major heads viz. impacts on ecology, on agriculture and on health, which are summarised below:
• Ecological Hazard: Parthenium is replacing the dominant flora in a wide range of habitats. Wherever it invades, the weed forms a territory of its own replacing indigenous grasses and weeds which are useful for grazing animals and ecology as a whole. This plant has no natural predators and sheep, goat or cattle do not feed on it. As a result, the food chain gets disturbed – the trophic structure changes and the region teeters on the brink of an ecological disaster. It is thus a strong threat to bio-diversity. Very little or sometimes no vegetation can grow in congress grass dominant areas. Strong allelopathy potential is also reported. Allelopathy is a phenomenon which can be described as the release of chemical substances from the plant into the environment as a consequence of which the growth of neighbouring vegetation gets adversely affected
• Agricultural Hazard: In agriculture, the weed’s twofold impact results in reduction of crop yield by its ecological aggressiveness on one end and finds itself mixed with the crop, particularly, in kharif fodder crops like jowar on the other. With the fodder it reaches cattle and its toxic elements enter the food chain which is manifested in the milk it produces.
• Health Hazard: Several health problems have been reported in human population exposed to its infestations. Farmers while working on their fields come in contact with Parthenium and are subjected to various skin problems including itching, particularly of the eye and other allergic symptoms. This plant also triggers asthma because its minute flowers and pollen are readily dispersed into the air.
Besides all above mentioned threats, the problem of Parthenium is much more complex. It’s expansion may be compared to a raging forest fire and no strategy till date has been successful enough to check the expansion of this invader. The pesticides recommended by agricultural scientists for the elimination of it are very costly and small farmers are not able to use them.
After extensive research and experimentation in various districts of Haryana, scientists from Ch. Charan Singh Harayana Agricultural University, Hissar have suggested that this weed can be effectively checked by the pesticides like Glaiphoset and Matribuzin. But there are various arguments against prolonged use of chemical pesticides because of their adverse effects.
Using a biological method of controlling weeds it has been found that a plantation of Casia Siresia in congress grass affected areas can check its expansion. After a few years it can even be completely eliminated. However, this process is slow and the danger of replacing a weed by another weed cannot be ruled out. Another biological control of it is an insect known as the Mexican beetle. Use of this beetle was found to be successful after trials in some parts of Jammu and north Haryana. Biological invaders are deadly and effective environmental measures need to be stepped up to check their expansion.
Awareness is the first step in eliminating this infestation.