Weed management in Bt cotton is achieved through a combination of methods that include, cultural mechanical and chemical approaches. In many parts of the world, chemical control of weeds with herbicides is the predominant method of weed management notonly in cotton but also in major commercial crops. Currently, worldwide, herbicides outrank insecticides andfungicides in both volume used and total sales. As use of herbicides has increased, more and more cases of resistant weeds have been documented.Since the first reported case of weed resistance in 1970, 331 weed species so far have evolved resistance. To preserve the utility of herbicides in agriculture, active resistance management is essential, using methods such as herbicide rotation, mixing herbicides with different mechanisms of action, combining non chemical methods like solarization, mulching with organic and inorganic mulches, stale seed bed technique, mechanical removal growing compatible intercrops as smothering crops and combination of all the above techniques wherever possible keeping in view of the environmental safety and sustainability of the system Although, herbicide tolerant genetically modified (HTGM) crops offer broad spectrum weed control encouraging the farmers to adopt reduced - or no-tillage operation, eliminating the use of some of the environmentally harmful herbicides, there is concern among weed scientists that over-reliance on fewer weed management strategies will result in evolution of resistance to the useful herbicides and/or population shifts to naturally resistant weed species. Recent advances in nano-biotechnology have potential to be explored in developing nano herbicides which can penetrate and kill the weed seeds preventing themfrom germinating into harrrful weeds. The micro encapsulation technology has good potential for controlled release of active ingredient for the extended period of weed control. As the world is gearing up towards challenges of climate change, the weed scientists should initiate anddesign weed control strategies to meet the challenges posed by weeds keeping the environmental safety at theforemost concern.
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