One nursery told me this was spider mites (it's not). Another said it was a fungus.
It's an Amur chokecherry. It's had this problem all 3 years since I planted it. It starts in mid-summer with dark spots on the underside of the leaf, then it turns yellow, then brown around the edges, then all brown. It progresses from the leaves nearest the trunk outward.
What sort of fungus would it be? Copper spray (every 7-10 days) had no effect last year. Watering with peroxide has had no effect, either. -- Julie
How do you know it isn't mites? It looks like mites to me also, they are impossible to see. Did you try bayer 3 in 1? it is a miticide, insect and disease spray? It has to be sprayed every 7 days for several weeks or so.
jill
I know it's not spider mites because there is no webbing. The first year I used an insecticide, but I don't remember which one. The second year I used the copper spray. This year I've been using garlic juice.
Julie
You don't always see the webbing with spider mites. Check for little teeny tiny brownish/reddish dots on the undersides of the leaves.
Hey ecrane, I agree was just going to mail your webbing info to her..guess we are in the helping mood today. I'm going to sign out and get outside with my plants
Jill
Thanks, both of you. The dots are readily apparent, even in the photo. Back to insecticide, I suppose. Happy gardening,
Julie
The dots may be a little too readily apparent in your photo--hard to say without seeing it in person but those dots might be a bit too big to be spider mites. You usually have to look really close to see them, although that is a nice closeup shot of the leaves so I suppose it's possible that's the mites. Do the dots rub off? If they're fungal then most likely they won't rub off, but if they're spider mites then you should be able to rub them off. Although rust would rub off too, so that test isn't 100% for sure. Best thing to do might be get out a magnifying glass, with that you should be able to see if there are little legs on them or not.
Tap the leaf over a sheet of white paper. See what falls off. Some of the small critters are best identified with a magnifying loop. A good investment for a gardener. A close examination using a loop of the spots can very often tell you if it's caused by a sucking or chewing insect.
