MSU Extension Gardening in Michigan

Just on a hike here at the Leelanau County Government Center at our nature trail. I noticed this thing that I wanted to show you here called Maple Erineum. This is something called Maple Erineum. It is a red velvety abnormal growth you might find on maple leaves. You can find this on lots of landscape plants, but here we're seeing it on maple. Erenium is just a word for this kind of almost velvety abnormal growth pattern you might see on lots of different plants in the landscape. It's caused by a mite, a tiny mite called an eriophyid mite. And what's actually happening is the mite is feeding on the leaf and stimulating the leaf to produce trichomes, which are those tiny little hairs on a plant surface. Those trichomes when they're produced in abundance like this, create that velvety appearance, and it creates a shelter for the mites, protects them from predators and other things. As bad as it might look or abnormal as it might look, I guess, this actually looks kind of cool. But, you know, it doesn't always look like this on all plants, and it might be an undesirable appearance. But it doesn't actually harm the tree very much. The mites aren't taking a lot of the resources. This maple tree has got plenty of energy that it's gathering from the sun to be vigorous and healthy. And this parasitism by the mite really isn't harming the plant all that much. And usually we'll see these things kind of come and go as their natural enemies, other mites that might eat them or insects and things that naturally prey upon those mites, knock their numbers back down and they'll come and go. There's another problem caused by mites on the same maple tree here. This is called a maple spindle gall. These are young, just getting started out. We're early in the season. Later in the season, these spindle galls can be a little bit more noticeable. But these are also caused by a similar mite, a mite that causes the tree to grow abnormally and create a shelter for it. But both of these problems caused by mites are really more of a nuisance than anything else, and you can kind of notice them. Maybe point it out to your friends as a curiosity, a topic of conversation and let it go.