Other broods spend 2-4 weeks in this stage during the season. The first noticeable damage from onion maggot injury is the wilting of foliage. The plant eventually becomes flaccid and collapses. This type of damage is very noticeable when the plants are seedlings. Larger onions usually survive the attack although distorted and rotted growth makes them unmarketable.
Most damage is noticed in the spring.
The damage inflicted by the maggot can introduce and spread certain fungus and bacteria rots of onions. Locate new plants in a part of the garden different from the previous year's location. If that is not possible, remove infested soil and replace with fresh soil. For control in onions apply diazinon as per label instructions. Treat at planting time.