Q. I noticed that some of the leaves of my elephant garlic are wilting to one side. I pulled two plants and saw maggots, which I believe are called onion maggots. I have garlic that never sprouted and they had maggots as well. I then decided to pull out all my elephant garlic and most of them were infested and rotten. These maggots also seemed to feasting on my organic fertilizer that I applied.
What do I do next? Is it okay to plant other plants in there? Will these maggots be damaging to plants such as peppers, tomatoes, squashes and other non-root crop plants? What is the best way to prevent something like this from happening again?
A. I am surprised you have onion maggots. This is the first time this has been reported to me in our climate. This is usually a cooler climate problem as they don’t seem to like high summer temperatures very much.
There are other maggots that attack seedlings. But if this maggot has attacked an onion bulb as it is bulbing up then it is probably onion maggot. Onion maggots need a source of food, onions, nearly continuously to survive.
Most control recommendations are to make sure that all onions and remnants of onions are totally removed from the garden area at the time of harvest. You cannot leave anything in the ground that is onion related.
Onion maggots don’t like garlic very much so it surprises me that they are in garlic as well. Your observation is correct, onion maggots do like heavily composted soils particularly when the compost has not had a good chance to break down.
Onion maggots cannot survive in the garden without some source of food for them. However, they can survive during the winter for a longer period of time without food than they can in the warmer months.
I would recommend that you plant garlic and onions in rotation with other crops and not plant them continuously in one spot. It is okay to replant onions and garlic in the same spot after about three years. Make sure during your growing season that you have a good solid break from all onion related crops for at least two months before replanting onions or their relatives.
I am told that you can plant radishes as a trap crop, attracting the maggots to the developing radishes rather than the onions. The radishes are harvested when infested and destroyed.