Parthenium-a threat to agro-ecosystem


Dr Banarsi Lal

Union Territory of Jammu and Kashmir is situated in Northern most part of India and its major part is situated in the Himalayan region. J&K is blessed with immense natural beauty and is considered as the heaven on the Earth. Most of its land is under orchards, pastures, grasslands, forests and wasteland ecosystems. As most of these lands are not used for frequent cultivation, the obnoxious weed like Parthenium hysterophorus (Congress grass) has invaded most of these lands. Parthenium weed is regarded as the worst weed because of its invasiveness, potential for spread and economic and environmental hazards. This invasive weed is presently found in almost all the parts of J&K causing a serious threat to the biodiversity of this beautiful part on the Earth. This weed is considered as the dominant weed in J&K as it has covered almost all the fellow lands, river beds wastelands, pasture lands, grasslands etc. It is a noxious weed because it is highly adaptable to almost all types of environmental conditions and can invade all types of lands, causes high losses in the yield of crops. This weed forms dense, impenetrable thickets and reduces the productivity of crops, pastures, orchards and forestry plantations by its competition for resources and allopathic effects. The low crops production and productivity due to this weed leads to scarcity of food, fuel wood, fodder, fruits, increase in monkey menace and migration of rural people to urban areas in search of employment after leaving the land fallow. About 80 per cent of population of Union Territory of J&K directly or indirectly depends on agriculture. People of J&K fulfill their subsistence needs from cultivated, uncultivated and degraded lands. Crops production and productivity can be enhanced in J&K by the management of this problematic weed with the effective technologies. It can be seen on roadside, railway tracts, vacant lands, wastelands, agricultural, horticultural and plantation crops, industrial areas, irrigation canals etc. in almost every district of J&K. There is need to understand the biology of this obnoxious weed, its ecological impacts and management techniques. This troublesome weed has high rate of dispersal and adaptation to adverse conditions. About 30 per cent of the land of J&K is under cultivation. This weed is now spreading rapidly its tentacles in agricultural lands, forests and pastures. It is spreading at an alarming rate in the J&K and is found in almost all the districts of J&K. This weed is inversely affecting the biodiversity and ecological system of the J&K. It is said that it was introduced in Jammu and Kashmir in 1963 from Madhopur in Punjab across Ravi river all along the national highway. After that it has been dispersed in all over the state. Presently its infestation is alarming as it has covered large area in J&K. It has been observed that this weed has reduced different crops yields and has also affected biodiversity in J&K.
Parthenium hysterophorus (Congress grass) is commonly known as carrot weed as its plant appears like carrot plant. It is herbaceous, an annual plant belonging to subfamily Heliantheae and family Asteraceae (Compositae). Its vernacular names are as Gajar Ghas, ragweed, white cap or top, Gajari, Chatak Candani, Nakshtra Gida, Safed Topi etc. This weed has been rapidly spreading from the last two decades across the J&K and now this weed has attained the status of “Worst Weed” because of its allopathic effects on different crops and harmful effects on human beings and animals. It has been observed that its infestation causes crops yield losses up to 40 per cent in several crops and reduces fodder production up to 90 per cent. It is an aggressive annual herbaceous plant which has been widely dispersed across J&K. This weed rapidly covers the new surroundings and poses a serious threat to the environment and biodiversity of J&K.
This dangerous weed has been categorized as “Cosmopolitan weed”, “National culprit” and “National health hazard” due to its serious environmental threats. Parthenium origin is considered to be Mexico. In India, its occurrence was first noticed in Pune (Maharashtra) in 1955 and now it has covered almost all parts of the country. It is supposed to be introduced in India from the United States of America along with wheat and other cereals import. By 1972, it had dispersed into the majority of the Western states/UTs from Kashmir in the North to Kerala in the South. It has widely spread in India from Kargil region to Port Blair in Andaman and Nicobar. This weed grows at a faster rate due to its aggressiveness, high vitality of seeds, easily dispersal, innate dormancy and prolific seed producing nature. Any part of the plant (even root) can cause the subsequent risk of allergic reactions. In humans it causes health hazards like skin allergy (dermatitis), hay fever, asthma and bronchitis with flowers, seeds and even hair on leaves. The skin becomes photosensitive making it hard for the patient to face the sunlight. Bare parts of the body, soft tissues around the eyes and under joints are more likely to be effected by the contact dermatitis. Allergic papules are observed in school boys when they volunteered for uprooting parthenium.
Animals are equally prone to the harmful effect of the weed. During summer seasons, when the animals do not get palatable species in grazing lands, they are forced to feed on parthenium. As a result milk taste becomes bitter and they suffer with ulcers in mouth and intestine. Whenever animals walk or graze through parthenium, their udders are inflamed and they suffer with fever and rashes. Histopathology of the kidney and liver revealed degenerative changes and necrosis. Being toxic to livestock ,causing both acute and chronic toxicity, a noticeable reduction in milk yield, tainting of milk with parthenin, de-pigmentation of skin, tainting in mutton and bitter taste of milk have been observed. The milk consumption of the animals grazing around parthenium invaded fields is hazardous to man. Some animals feeding on parthenium die due to acute dysentery, itching, cryhematous, development of oedema around eyelids, dorsum of tongue, loss of hair etc. Parthenin is the chief chemical (0.3 per cent) found in the weed.
Community efforts involving all sections of the society are needed to manage the parthenium. Uprooting the weed manually when the soil is wet and slashing with word, collecting and burning the weed before flowering are some of the means of its manual control. Spraying of a solution of common salt (Sodium Chloride) at 15-20 per cent concentration has been found very effective. Applications of herbicides like glyphosate (1-1.5 per cent) for total vegetation control or metribuzin (0.3-0.5 per cent) if grasses are to be saved in non-agricultural land are considered effective in preventing this weed spread. It can also be controlled by the use of bio agent Mexican beetle (Zygogramma bicolorata) as it is natural, self sustaining, inexpensive and is ideally suited to non-crop situations and wastelands. This bio agent remains most active during rainy season and it completely controls the weed. The plant species like Cassia tara, Cassia seriea, Amaranthus asper, Malva pustulata etc. have capability to replace parthenium. The other way to manage parthenium is by uprooting it before flowering and make vermicompost by pit method. Vermicompost can be applied in different crops to mitigate the nutrients problems. It can also be used in papermaking, an antifeedant and phagostimulants. National Research Centre for Weed Science, Jabalpur (MP) organises many awareness programmes on Parthenium eradication throughout the country by involving Krishi Vigyan Kendras, institutes under ICAR, environmental agencies, NGOs etc. Parthenium eradication has become a challenge in J&K because of its epidemic proliferation and strong reproductive potential. This weed is spreading at an alarming rate in J&K and some strenuous and strategic efforts are needed to eradicate this menace so as to improve the production and productivity of different crops. Both public and private organizations need to work together to manage this obnoxious weed.
(The author is Head, KVK Reasi).