Author(s):

Dr. RR Upasani and Dr. Sheela Barla

Abstract: Resistance of weeds to herbicides is not a unique phenomenon. The first report of insects resistant to insecticides was in 1908, plant pathogens resistant to fungicides in 1940, and of weeds resistant to herbicides (Triazines) in 1968. Herbicides are considered to be among the most widely used pesticides. However, over-reliance on them and absence of any preventive or other cultural practices resulted to the evolution and spread of herbicide-resistant weeds. Development of herbicide resistant biotypes may be threat to successful crop production. Resistance to herbicides is a serious problem worldwide. The cases of resistance are increasing at an alarming rate. Cross and multiple resistances have further complicated the situation. Though arrival of new molecules with different mechanisms of action can help overcome present cases of resistance, an overreliance on chemical weed control will continue to give rise to cases of resistance. Therefore, alternate management strategies must be developed to combat resistance. Resistance management requires both preventive as well as reactive approaches. Prevention will include suitable combinations of weed management methods such as cultivation practices, crop rotations, field scouting and herbicide rotations. Seed production by suspected resistant biotype should be checked to prevent spread of resistance to other areas. Crop production programmes worldwide have been focusing on techniques and issues such as conservation tillage, sustainability of resources, resource use efficiency and most important of all, the changes in global climate. Therefore, integrated approaches involving judicious combinations of cultural, mechanical, biological and crop and herbicide rotations must be adopted to reduce the dependence on herbicides. Tillage method, planting time, method of herbicide application, optimum dose, stale seed bed and zero tillage are some of the short duration resistance management strategies. Allelopathic cultivar development could be another strategy to mitigate the herbicide load. Rapid resistant screening techniques should be developed which requires simple methods yielding quick results. Physiological and biochemical studies will be helpful to develop such screening techniques.

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