Need help identifying possible leaf miner?

Question: Hi there- I have a lot of these flying insects in my caterpillar tunnel. It started in my spinach. I can’t tell if maybe it is a leaf miner? Even though it is currently in my leafy greens, I’m actually most concerned about identifying the ALF as soon as it starts flying and laying eggs. Thanks!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied February 27, 2023, 4:44 PM EST
response: Our vegetables specialist is confident this is not Allium Leafminer but instead is an adult Seedcorn Maggot. If you are curious about management options (of which, unfortunately, there might not be many), we recommend inquiring with U-DC's Extension program since they may be more experienced with techniques that have worked well in the city. (Granted, the insect's life cycle will be essentially the same here in Maryland, but the urban heat island impacts might be extending or shifting forward this pest's season of activity.)  Miri

responder: The Question Asker Replied February 28, 2023, 9:32 AM EST
response: I appreciate the quick response. I've never heard of or seen the seedcorn maggot before so that would have taken me a long time to figure it out. That's funny that you think the people at UDC-extension can help me. I'll try online resources.On Mon, Feb 27, 2023 at 4:46 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied February 28, 2023, 10:19 AM EST
response: The two pigmented spots on the fly's wings don't seem to match the all-clear wings of Seedcorn Maggot adults, so we're not completely certain that is what the fly is, but that was the impression our vegetable crop specialist had from the image and description. You may want to keep a sample or two of the adult flies if the DC specialists (should you did decide to reach out to them) wanted to examine them in person, since flies of this type can really best be identified to species-level detail with microscopic examination.  Another alternative is to have an IPM scout for hire (someone who uses methods other than insecticides, where possible, to manage pests and diseases) submit the samples to a diagnostic lab if they are connected with one. You're of course welcome to use our Maryland Vegetables web content (which is geared to commercial growers as opposed to home gardens) on our website, and a handy resource for common vegetable pests and their organic management is Penn State Extension's publication Vegetable IPM with an Emphasis on Biocontrol, which runs about $15.  Miri

responder: The Question Asker Replied February 28, 2023, 10:29 AM EST
response: I put one in a ziplock bag. Can I send that to you to be sure? In response to your first email which referenced the possible climate difference between DC and outer lying areas - it is true that this field is in DC (though I also manage 5 acres in Maryland.) But I don't think that is the cause for an early appearance of flying pests. This particular problem is happening in a tunnel so the ground never froze. It does very much feel like early spring in there.And because of the mild winter, the truth is that I never had frozen ground for more than 36 hours at a time. I anticipate having a lot of pest problems this year.On Tue, Feb 28, 2023 at 10:19 AM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied February 28, 2023, 11:48 AM EST
response: Insects would still go through a cold dormancy period to mature into adults the following year, so won't necessarily need freezing temperatures to do that and stay dormant during that time. Still, yes, warming temperatures earlier than usual, or an environment with sheltered conditions as you mention, could certainly speed that development up so that adults are emerging earlier than they would be in an outdoor and more rural environment. Fortunately conditions that benefit insect pests can also benefit some of their predators, since other insects are also temperature-dependent, so a pest outbreak one season might be followed closely by a population boom of their key predators or parasites, so there's still hope natural controls will catch up with them before they can cause too much damage.  Our plant diagnostic lab tells us they can accept samples from D.C., so you can submit the flies to them for ID. The lab manager says to submit the flies (several are preferable in case key body features are damaged on some of them) in either a vial of ethyl alcohol (don't substitute isopropyl alcohol unless they say it's ok) or send them dry in a plastic bag with plant material (if they are associated with plant material at this stage, or if they are causing plant damage). You can contact the lab manager through the page linked above if you have further submission questions about to include and how; the page also provides the submission form.  Miri