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Past Articles Library | Organic Pest Control | Control Onion Maggots



 

ONION MAGGOTS
(Delia antiqua)

Onion maggots are serious pests, and once they get established they are tough to get rid of. They burrow into developing onions and a single maggot can kill over a dozen seedlings during it's development. In addition, these pests can have two to three generations per year so they are a constant threat to onions, shallots, garlic, and leeks. Infestations are worst in cool, wet weather so damaged bulbs often rot.

 
 

DESCRIPTION

Adults are gray flies, 1/4 inch (6 mm) long. Larvae are white maggots, 1/3 inch (8.5 mm) long, and are found burrowing in onion bulbs.

 
 

LIFE CYCLE

Pupae overwinter in the soil. Adults emerge from mid-May to late June and lay eggs at the base of plants. Eggs will hatch in a week; maggots will then burrow into roots for two to three weeks, then pupate in the soil nearby. Adults emerge in one to two weeks. These pests can have two to three generations per year.

 

 

 

PLANTS MOST AFFECTED

Onion, shallot, garlic and leek.

 

 

DAMAGE

Maggots burrow into developing onions, killing young plants and hollowing out or stunting older plants. A single maggot can kill over a dozen seedlings during its development. A late generation may also infest onion bulbs in storage.

 
 

ONION MAGGOTS CONTROL

Prevention:

1.Use sticky traps. Yellow sticky traps will capture the flies in the spring. Tanglefoot is also a good organic substance that can be safely sprayed or spread on stems and catches anything that climbs up.

2. Rotate crops.

2. Cover seedlings with Floating Row Covers to keep adults from damaging plants.

3. Plant onion sets late to avoid first generation.

4. Plant red onions and Japanese bunching onions, which can be somewhat resistant.

4. Sprinkle rows liberally with ground cayenne pepper, ginger, dill, or chili powder to repel females and prevent them from laying eggs.

Control:

1. First thing to do - get rid of as many maggots that are still in the soil as possible.

Depending upon how large your area is, remove the infected soil from the sites you have planted onions and had problems in the past. Replace it with clean compost. Then go to step 4 below.

If you can't remove the soil because the area is too large, then:

2. Drench the soil with this mixture:

3 hot green peppers (fresh or canned)
3 medium cloves garlic
1 small onion
1 tablespoon (15 ml) dishwashing soap
3 cups (720 ml) water

Puree peppers, garlic, onion in a blender. Pour the mixture into a jar and add the dishwashing soap and water. Let stand 24 hours. Strain out the solids and pour the liquid into a bottle and drench your soil.

3. Next get some insect parasitic nematodes that control maggots at your garden center and apply them to the soil as directed on the package.

You've now done about what you can to clean the soil of the maggots, the next step is to keep them out.

4. Cover seedlings with Floating Row Covers to keep the female flies from laying more eggs and starting the whole process over again.

You can also sprinkle your soil liberally with ground cayenne pepper, ginger, dill, or chili powder to repel the females.

5. Lastly, at the end of the season, make sure you get all onions, dead or alive out of the ground. You don't want to give the hibernating maggots a winter food supply.

That's about all that can be done for onions grown in the ground. As an alternative, try growing onions in containers or raised beds with fresh soil as last resort.








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