+1 on borers staying near the surface, basically in the sapwood. The distinctive tunnel made by the emerald ash borer is D shaped. Most insect tunnels are round. Powder post beatles leave a round tunnel and fill it with the powder they excavate as they travel. There are myriad insects this could be, none of which are good for your shop. You can exterminate these types of bugs only by heating the wood to near boiling point until the center is over 200° for an hour or so. Insecticides do not penetrate far enough, even the vaporous ones. YMMV, but that's what I've been told by experts.
Powdered Borax scattered around your wood pile will discourage new infestations and minimize spiders too.
It's kind of hard for me to tell from the pics but I see some very similar characteristic markings in ash which I never thought of as bug trails but could be, I suppose. However, I have wondered what causes them. I've not known it to be anything but solid. Are yours loose, or voids ?
Where do you get your wood? Is it locally sourced? Most states with Emerald Ash Borer infestations have placed quarantines on the wood to control the spread. In Ohio, unfinished Ash wood cannot leave the county where it was cut, that includes everything from firewood to fine quality lumber and construction materials. Finished (sealed) pieces like furniture and cabinets can still be shipped, but In Kentucky the Louisville Slugger company was having trouble getting raw materials because of quarantines. Expect the quarantines to be extended this year, as last summer they found that the Emerald Ash Borers were infecting other species of trees, also a fungal blight spread by beetles is damaging walnut trees.
Are Ohio's counties still quarantined? I remember seeing the signs a few (3-5) years ago then they disappeared. As I understand it, that requirement was lifted as the beetle was in every county in Ohio anyway, is this not correct?
You are correct bigblockyeti, I just checked the Ohio Department of Agriculture website and the intra-state quarantine has been lifted (although Montgomery and Greene Counties were still telling residents not to take the wood out of the county as late as last month). ODA urges caution before moving wood between counties, and says to contact them with questions about moving wood out of state. Local park districts have been cutting down a lot of ash trees then letting residents pick up free firewood, a park near my house lost almost all the trees.
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