Weed Management





	Tea Board of India, Ministry of Commerce and Industry, Govt. of India, AB Path, Kurseong , West Bengal, 734 203
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	Weed management
		Weeds are plants, usually herbaceous, growing in an area where they are neither desired nor appreciated. They grow in the fields where they generate formidable competition with tea bushes for nutrients, space, air, light, moisture particularly during drought and when plants are small, thus reduce crop yields. Weeds harbour insects and diseases for which they serve as alternate host. These apart weeds restrict branching and development of frame in young tea and reduce plucking efficiency due to growth of creepers and thorny weeds. Weeds growing within tea bushes if plucked inadvertently with tea leaf (such as Ageratum conyzoides Linn., Eupatorium odoratum Linn., Artimisia vulgaris Linn.) may affect quality. It also acted as hosts of nematodes in the nursery. Weed growth block the drainage and impede the flow of water in the transport channels in the fields. It also protects the pests and prevents the pesticides from reaching them. Weeds are not a major problem and regular weeding is not necessary in mature tea as its canopy cover the ground. But young tea plants may suffer a permanent setback in vigour if proper weed control measures are not taken at the appropriate time. The critical weed competition period in young tea was found to be in between April and September Weeds, by covering the ground, check oil erosion on sloping land like Darjeeling and other hilly terrains. It also helps in preserving soil structure and regulating fertility. Weeds are used for making compost in the plantation.
		Manual or mechanical methods In tea, hand weeding, sickling, cheeling, forking and mulching are the convensional methods of weed control. Hand weeding is carried out in the nurseries and the newly planted tea areas where application of any chemical herbicide is hazardous for the plants. Cheeling or surface scrapping is an efficient means of suppressing weeds with a minimum of soil stirring. This operation is carried out mainly to remove shallow rooted weeds when their density is rather high and a large area to be weeded. In Darjeeling hills, the concept of 100 % weed control is likely to increase the problem of soil erosion. Under such conditions the aim should be to control noxious weeds but leave a non-competitive ground cover of soft weeds. Mulching very effectively suppresses weed growth. Thatching and mulching in the clearings play an important part in weed control in young tea until the tea plants themselves are well developed and cover the ground. The vacant areas in the field should be rehabilitated by planting to Guatemala grasses (Tripsacum laxum) for one to three years. This will help in keeping the weeds under control, protect the soil from erosion and rehabilate the soil for infilling. In the nursery, planting of tea leaf cuttings by inserting through a black polythene mulch beneath a cover of hoop-supported polythene cloth has been reported to provide satisfactory weed control. In young and mature tea fields, mulching with black low density polyethylene (LDPE) sheet was also found very effective for control weeds.

	Chemical methods Controlling weeds manually has become increasingly expensive and there is often a shortage of labour during peak cropping season. To cope up with the problems, herbicides were introduced in tea industry with satisfactory results. However, manual weeding should supplement chemical weed control and be a part of an integrated programme. Though chemical weed control initially more expensive than mechanical or manual control but in the long run, rational application of herbicides can only optimize weed control. The success of a herbicide weed control depends on the identification of weeds, right choice of herbicide, dosage and time of application, and their use in suitable mixture. Weed management has to be such that it does not encourage soil erosion. In Darjeeling hills, chemical weed control was not recommended till 1960s apprehending soil erosion. It was suggested use of weedicides in Darjeeling tea area having 45% slopes or less and adoption of chemical weed control programme in combination with in situ mulching of pruning litter. However, herbicides should be used till June and then from September onwards to ensure that weeds do not compete for moisture in the cold weather. Herbicide can be given around the collar or in alternate strips in less sloppy areas even in the rains. Only sickling can be done in areas vulnerable to erosion.