Allium caesium · Bulb
Allium leaf miner: Cover plants with fine insect-proof mesh during peak fly activity in spring and autumn.
Onion white rot: Remove affected plants immediately and avoid replanting alliums in that soil for many years.
Onion fly: Use insect-proof netting to exclude adult flies during their spring emergence period.
Downy mildew: Improve air circulation and avoid overhead watering to keep foliage dry.
Slugs and snails: Use physical barriers like copper tape or apply iron phosphate-based pellets around the base.