Help! White larvae falling from Doug Fir branch #863158

Asked April 02, 2024, 3:44 PM EDT

Hi! I live in Portland and have a big healthy dog fir tree in my backyard. There is a large branch that hangs over my patio and over the past few days white larva have started falling from it. I don’t know how serious the problem is or what kind of insect they are, but there are hundreds alljj be over my deck! An arborist said the tree looks healthy last month, but I’m wondering if you can help me identify these and advise? Thank you!

Multnomah County Oregon

Expert Response

Hi Karen,
Those are fly larvae (Order: Diptera). I cannot tell for sure what type of fly larvae they are from the photos though. To be certain, I'd have to look at some specimens up-close in person.
However, I suspect that they could be blowfly larvae (Family: Calliphoridae) or flesh fly larvae (Family: Sarcophagidae). Here are links to some photos of the larvae of those types of flies for comparison....
Most blowfly and flesh fly larvae are scavengers that feed on dead animal carcasses. Lots of these larvae can develop on a dead animal. Then, once the larvae are fully mature, they move away from the carcass to find a place to pupate. So, I suspect an animal died up in your tree, the larvae developed there, and now they are dropping down to find places to pupate. If this is the case, there will be fewer larvae falling down over time and the problem will go away after the tissue on the carcass is fully consumed.
If you are continuing to find more larvae after a week or so, and want to confirm what type of larvae they are, you could send some specimens to us at the OSU Plant Clinic for identification. Here is a link with information on how to submit a sample if you would like to do that....
Bill Gerth Replied April 02, 2024, 5:38 PM EDT

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