Which borer is this?

I met a borer I had never seen before...
While inspecting a young apple tree yesterday, the trunk simply broke off at ground level upon touching it... There was simply no more wood, just a thin layer of external bark holding.

This guy was about 3/4 inch long and definitely yellow. All the borers I have seen yet were much smaller (like usually about 1/4 inch long) and white, so I am wondering who is this guy... Also there was no characteristic reddish frass.

Here are photos:
1- a section of the stem with the end of the borer sticking out


2- opening-up the stem


3- close-up of the head


PS, it seems we need to click on [open image URL] link to see the photos.

Jolicoeur Orchard
Zone 4 in Quebec
Author, The New Cider Maker's Handbook



Edited 2 time(s). Last edit at 05/02/2022 06:53AM by Claude Jolicoeur.

That sure looks like a roundheaded borer to us. We've never had them in our orchard to have direct visual experience (we tend to have dogwood borers and peachtree borers get in our apples, and this looks like neither of those). However, the size of the borer in your picture is staggering to us -- our dogwood and peachtree borers are much smaller -- and it sounds like roundheaded borers would usually be smaller, as well, though they may grow 2.5 cm in length. But given that roundheaded borers can live in the wood for 4 years, perhaps you've got a great granddaddy with some girth on your hands?

A resounding ugh. Good luck.

Kordick Family Farm
Westfield, NC
Zone 7a