Identify pest

Question: Hello, I am hoping to identify these pests. They appear late summer and into fall and have been getting worse the last 2 years. Besides eating the leaves on some of our Dogwood bushes they literally are eating our house. In a matter of minutes they can bore into a 2x4 deck railing or 6x6 post, they also eat the siding and trim boards. They come out of the lawn next to the porch and the rock areas next to the house. I killed hundreds last year with dish soap and water in a pump sprayer but they just keep coming during the day. They are about 3/4" to 1" long when fully grown. Any help to eliminate them is greatly appreciated so I don't have to replace any more siding or trim boards, thank you. Mark

responder: An Ask Extension Expert Replied April 16, 2024, 4:36 PM EDT
response: Hi Mark, I believe you've observed the larvae of the dogwood sawfly (Macremphytus tarsatus). Despite resembling caterpillars, they are actually the larvae of a type of wasp.  The best way to manage these wasp larvae is by spraying them with insecticidal soaps/horticultural oils (which work better than dish soap). And it is imperative to make those applications when the larvae are less than an inch (25 mm) long. Once larvae pass that size threshold, they become more resistant to insecticides. This spraying can be supplemented by shaking them off plant material and crushing them underfoot.  After they've finished feeding, the larvae seek out decaying or soft wood to burrow into for pupation. If the wood is pressure-treated and properly preserved, these insects will have a very difficult time boring into it. Identify, remove and replace any rotting/soft wood. Wood-boring insects typically cannot infest pressure-treated wood. But if they infest the wood prior to treatment, they may emerge from the wood following pupation.  Let me know if you have further questions.

responder: The Question Asker Replied April 16, 2024, 4:46 PM EDT
response: Thank you for your response     Get Outlook for iOS  From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>> Sent: Tuesday, April 16, 2024 2:36:29 PM To: Mark Kellner <<personal data hidden>> Subject: Re: Identify pest (#0134679)

responder: The Question Asker Replied April 16, 2024, 8:11 PM EDT
response: Just for your info, they will bore right thru 2 coats of paint and into solid wood and siding that is structurally sound  Mark     Get Outlook for iOS  From: Mark Kellner <<personal data hidden>> Sent: Tuesday, April 16, 2024 2:44:23 PM To: Ask Extension <<personal data hidden>> Subject: Re: Identify pest (#0134679)    Thank you for your response     Get Outlook for iOS  From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>> Sent: Tuesday, April 16, 2024 2:36:29 PM To: Mark Kellner <<personal data hidden>> Subject: Re: Identify pest (#0134679)

responder: An Ask Extension Expert Replied April 16, 2024, 8:27 PM EDT
response: Wow, that's impressive. I will run your question by my entomologists colleagues to see if they have a different ID/control recommendations. I will let you know if they say something different than what I said.

responder: The Question Asker Replied April 16, 2024, 9:31 PM EDT
response: Thank you. I appreciate your help.    Get Outlook for iOS  From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>> Sent: Tuesday, April 16, 2024 6:27:21 PM To: Mark Kellner <<personal data hidden>> Subject: Re: Identify pest (#0134679)

responder: An Ask Extension Expert Replied April 17, 2024, 4:27 PM EDT
response: Hi Mark, I heard back from my colleagues. They agreed with my ID and the management, but had two things to add. 1) these sawflies can bore into wood that is structurally sound. So the issue is not that the wood has rotted, as you pointed out. 2) the wood can be treated with a residual insecticide to prevent wood-boring. However, I would only apply this when the larvae are mature and are looking for somewhere to bore into (late spring/early summer). The best estimation of when to apply would be when you see larvae over an inch long, or around late July/early August.  By residual insecticide, I mean one that sticks around for a while. Cyfluthrin is one option. There are other insecticides in the Permethrin class that may work. You'll know it's a permethrin because the active ingredient ends in -"thrin".  When applying these insecticides, make sure to follow the instructions on the label exactly. Also, try to avoid applying these insecticides on hot or windy days, and not when rain is expected in the following days.  I hope this helps!

responder: The Question Asker Replied April 18, 2024, 11:17 AM EDT
response: Thank you for your continued responses and suggestions. Last fall we heavily pruned back the very large Dogwood bushes and remove a lot of dead branches. I purchased Bio-Advanced hose sprayer insecticide to spray around the shrubs on the ground and the leaves after they leaf out. It says it will work for 14 days and not affected by rain. I will look for what for what you recommended to spray on the house after they appear.Thanks again, MarkOn Apr 17, 2024, at 2:27 PM, Ask Extension <<personal data hidden>> wrote: