Trying to identify flies in garden - Ask Extension
Hello,
This past week, I planted a number of seeds in containers (onions, fennel, leeks, kale, sage, dill, and chives). To the extent that it matte...
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Trying to identify flies in garden #822204
Asked March 11, 2023, 3:33 PM EST
Hello,
This past week, I planted a number of seeds in containers (onions, fennel, leeks, kale, sage, dill, and chives). To the extent that it matters for my question, I'm using a combination of Harvest Organic Potting Mix and Dr. Earth Vegetable and Herb Fertilizer. I have noticed in the afternoons a number of flies around the soil. I only notice them in the afternoons. They also seem worse when the soil is more wet than dry. They don't look like normal house flies. When I Googled the issue, I see many results for fungus gnats. However, it sounds like they are smaller (like a fruit fly). These are bigger than a gnat, but not as big as a house fly. They don't fly around very much. They mostly just walk around the top of the soil. But if you bump the container, they certainly can fly. I've attached a picture of one on my patio.
My concern is that these flies are actually in the soil. If they are simply attracted to the fertilizer, etc., then no problem. Any help with identifying the type of fly/insect, would be much appreciated.
Henrico County Virginia
Expert Response
I am not able to ID from this picture. It is hard to see details of the fly on the stone patio. Could you take another image of the fly on a white background and include and object for scale?
Hello,
It is a little difficult to get the fly on a white background. I tried to take some better pictures with some perspective for scale. Attached is one picture of the fly on some brick and two (2) pictures on a plastic, terra cotta colored container. The terra cotta colored container is 22"L x 8" W x 6" H for scale. Thank you again for any help that you can provide!
Our entomologist was able to identify this fly as seed corn maggot. You would not expect to find this is fresh soil, so did you use old soil, or are there containers were there is old soil in them that could have had the eggs in it? The fly is not the concern, the larval (maggot) stage is the problem.
The adult flies will lay eggs in the fall on on the soil surface near sprouting or decaying seeds, organic plant residue, or organic soil amendments. Those eggs will hatch in the spring and the fly maggots burrow downward in search of food and penetrate seeds as the seed coat splits open. They hatch out in early spring and seek out vegetables and field corn growing in cold damp soils. The maggot stage feeds on cotyledons and small roots and cause stunting, yellowing, and death of small plants. Seedcorn maggots are most damaging when spring weather is cold and rainy.
Cultural control:
Avoid seeding too early. Seeds germinate more quickly and are less vulnerable in warmer soils. Be patient!
Used raised beds so that the soil is warmer and the plants grow faster than the seedcorn maggots can damage the roots. Replanting works well as only the spring generation is damaging. If you need to replant, wait at least 5 days if maggots that you find are a quarter inch long; if they are smaller than that, wait at least 10 days to make sure they have pupated and will not damage the new seeds.
The adult flies will lay eggs in the fall on on the soil surface near sprouting or decaying seeds, organic plant residue, or organic soil amendments. Those eggs will hatch in the spring and the fly maggots burrow downward in search of food and penetrate seeds as the seed coat splits open. They hatch out in early spring and seek out vegetables and field corn growing in cold damp soils. The maggot stage feeds on cotyledons and small roots and cause stunting, yellowing, and death of small plants. Seedcorn maggots are most damaging when spring weather is cold and rainy.
Cultural control:
Avoid seeding too early. Seeds germinate more quickly and are less vulnerable in warmer soils. Be patient!
Used raised beds so that the soil is warmer and the plants grow faster than the seedcorn maggots can damage the roots. Replanting works well as only the spring generation is damaging. If you need to replant, wait at least 5 days if maggots that you find are a quarter inch long; if they are smaller than that, wait at least 10 days to make sure they have pupated and will not damage the new seeds.
