Crop-weed interactions and their management under climate change: A review

Weeds pose as biggest threat to crop production accounting about 43% yield loss globally. Unchecked human activities such as over-expanded use of fossil fuels and deforestation have resulted in climate change which further worsens the present situation by impacting both crop and weed. Predicted alteration in atmospheric CO2, temperature and frequent extreme events (e.g., droughts and floods) owing to climate change will reduce crop yields by affecting plant growth as well as pest pressure (weed, insect pest and pathogens) and their invasiveness, thus threatening global food security. CO2 fertilization due to rising CO2 level will benefit C3 crops, thus reducing the competitive ability of most of troublesome weeds which are C4 plants. However, weeds are predicted to become more competitive over crops owing its wide genetic diversity, colonising ability and enhanced aggressively of C3 weeds consequently making weed management in field situations costlier and more difficult. Change in environmental factors like temperature, atmospheric humidity, elevated CO2 and soil moisture can manipulate efficacy of various weed control measures like mechanical weed control, herbicides and bio-control agents. Extensive research and evaluation of new herbicides, higher chemical concentrations and new bio-control agents will be required for managing weeds under this scenario. Adoption of ecological approaches (crop rotation, intercropping, live mulching, early planting of crops, nutrient management, selection of suitable crop varieties), improved tillage practices, genetic improvement of crops (breeding allelopathic crops cultivars and drought- and stress resistant varieties) may enable to reduce weed problem. Holistic weed management will be the need of the hour for tackling weed menace in this context.