What's eating my onions?

Onions are troubled most by onion fly (whose maggots destroy bulbs), thrips that scar leaves in dry weather, and allium leaf miner in the UK. Onion white rot is the most devastating soil disease. Slugs attack seedlings. Birds occasionally pull up transplants. Crop rotation and insect-proof mesh are the most effective defences.

Yellowing, wilting leaves on young plants; white maggots tunnel into bulb bases causing rot and plant death Cover with fine insect-proof mesh (50-mesh) immediately after planting; avoid using nitrogen-rich manure that attracts egg-laying flies; rotate onion family to a new bed each year

Silvery streaks and flecking on leaves; distorted growth; heavy attacks reduce bulb size Use blue sticky traps to monitor; apply insecticidal soap or spinosad spray; ensure adequate irrigation as drought stress worsens thrips damage

White dot-puncture rows along leaves made by adult fly; cream maggots mine into foliage and bulbs causing rot entry points Cover with insect-proof mesh during adult flight periods (March–April and October–November in UK); remove and destroy infested plant material