Well since vinegar is a weed killer not sure I’d go that route. Even if it does kill the tree it may cause a lot of stress and possibly long term death. And absolutely wouldn’t want it to get on roots as not only is it a weed killer but acts to severely dehydrate. Will vinegar kill mildew and mold certainly — I have poured household vinegar on my porch and watched it eliminate the mildew, mold, brush it with a broom and rinse and until it dries it looks like new fresh brown wood. Lichen is not an issue with trees, it isn’t a parasite. It’s not like moss, mildew, rot or mold that indicate a wet or damp condition that needs to be remedied. Lichen is simply a sign of old age even old rocks acts as a substrate for it. Someone said to me well my 100 yr old tree had it and it died. It was an Apple that hadn’t produced in 20 years and was 20-30 years past its natural life span. Most don’t live past 75-80 years rarely 50. It died of old age not the lichen. I have heard and seen some very reputable bonsai use a power washer to clean lichen off — I wouldn’t do that either. As pressure washers — really anything over about 40psi — strip bark and wood with the lichen and causes microscopic tears, crevices, holes, etc that allows viruses, fungus, and pests to take better hold. It amazes me that people would do this, the same folks that make sure they disinfect or heat treat pruning tools and they use expensive paste to seal up all pruning cuts to prevent disease and pests from attacking their beloved bonsai — are willing to rip the bark off the entire tree and leave it exposed.
You might want to look at spraying with Physan20 at the correct label and see if that would help. You can spray it and leave it. I use it on my orchids- go to the manufacturer’s website Physan.com and look under applications. It’s for use on ornamentals, African violets, orchids, etc in addition to disinfecting cutting tools, hands, pots, etc etc.
Since I understand the issue of if too heavy and being ugly - Here are couple of sites — Univ of PA, NJ Univ/Rutgers, Dept of Forestry and from a roof inspector. These give a brief explanation, biology of them, and should assure you, if your trees are healthy, growing well to leave them alone. Now if your tree is so old or you don’t like it that much, then by all means — treat it however, it’s your tree and if it dies, good riddance right. If your tree is diseased, full of fungal issues, pests invading it - then I would get immediate expert advice. If you go to removing the lichen, and covering it in vinegar, or bushing it off, you may expose it to more issues opening up microscopic pores. We have to remember, nothing lives for ever, not us, not trees, not anything. Like a roof that is covered in layers of lichen — it is probably well past it’s life expectancy and needs to be replaced before it starts leaking. However, the leaking probably won’t be from the lichen. And lichen can be growing in the same areas with bad issues like wood destroying fungi, moss which is thick and heavy, full of water, or mildew and mold.
Lichens are often thought to be a pest or disease to trees and shrubs.
extension.psu.edu
FS1205,
njaes.rutgers.edu
www.fs.fed.us
inspectapedia.com
