White rot on onions
Onion foliage turns yellow and wilts, then fluffy white mould appears on the base of the bulb.
Cultural control: No cure. Remove and destroy infected plants. Try sterilising ground before planting and ensure that you do not grow onions or related plants on infected ground. Avoid over feeding plants and only store fully ripe bulbs. Avoid bending the tops to induce ripening.
There is currently no chemical registered for the control of this problem.