How do I control canker and leaf miner in lemon (nimbu)?

Rough, raised, corky brown spots with a yellow halo on leaves, twigs and fruit are citrus canker, a bacterial disease that spreads in warm wet weather and through wounds. Manage it by using clean planting material, pruning out and destroying badly affected twigs, avoiding overhead watering, and protective copper based sprays following the label, especially after the citrus leaf miner damages the leaves. The wavy silvery tunnels in tender new leaves are from citrus leaf miner, and those wounds let canker enter, so controlling the miner on new flushes reduces canker too. Follow label doses and pre harvest intervals. Confirm the diagnosis and the latest recommended sprays with your KVK or horticulture office.