Grifola Frondosa (Hen of the woods) is a white rot fungus, It is what we call a saprophyte exploiting tree tissue dying from other causes. I also pick a large % of my hens from standing trees, but they are not healthy. If you look close at those trees you will see stress, most of the time it is heart rot. You would want to avoid drilling and plugging healthy oak trees. Also a stump or a tree that is not fresh cut most likely has been hit with a saprophyte fungus and not knowing which one I would avoid also. I got bees also and that wax could be used for better projects.LOL.. I have plugged thousands of logs ranging from shittake, lions mane, many strains of oysters, reishi and other wood lovers and never had a contam issue. Moisture is the key, keep those logs in a forest edge setting with that mixed light. I wish you the best of luck with your hen journey.