Pull up and destroy infected bulbs. Scatter onion plantings around the garden rather than concentrating them all in one bed. Hand pick bugs. Keep the garden free of debris and hiding places. Use trellises to raise the plant off the ground.
Plant marigolds, radishes, tansy or nasturtiums nearby.
Dust with wood ashes or lime. Use row cover. Ants Ants are attracted by 'honeydew' which is a sweet substance secreted by insects such as aphids. In fact, the damage that is sometimes attributed to ants is actually done by aphids. Treating aphids with a soap spray will encourage the ants to go elsewhere in search of a meal.