How to control late blight in potato (aloo)?

Late blight (Phytophthora infestans) spreads explosively in cool, cloudy, humid weather and can destroy a crop in days, so act on forecasts and at first sign. Begin protective sprays of a contact fungicide like mancozeb 75 WP at 2 to 2.5 g per litre before the disease appears, especially when weather turns cool and overcast. Once blight is seen or pressure is high, switch to a systemic plus contact combination such as metalaxyl plus mancozeb, then rotate back to contacts to avoid resistance; never use metalaxyl alone repeatedly. Spray at 7 to 10 day intervals, shorter in wet spells. Avoid overhead irrigation in the evening, ensure good airflow, earth up well, and destroy cull piles and volunteer plants that carry the fungus. Follow the label dose and pre harvest interval on every product.