I'm in the Orlando area in zone 8 (I think?) The magnolia tree on the rental property I live on is sick with some kind of fungus I think. It has spots all over about 15% of the leaves that look like mold or mildew. Can someone please help me identify what it is we're dealing with here? It's an absolutely gorgeous tree, I hate to see it suffering. And I'd like to inform the management company so that measures can be taken to bring the tree back into good health.
It looks like its suffering from a bad case of scale - an insect that secretes a shell over itself and sucks the sap from the leaves. They are hard to kill because of that little protective case. Think of them as armoured aphids.
It could be powdery mildew. Problem in SE. Lots of rain?? A sprinkler?? Dripping water from an overhead structure??
Not a ton of rain lately - no overhangs or sprinkler system either :/
I agree that from the picture it looks like scale. Scale insects are small dome-shaped bugs. You can check if it's an insect as opposed to a mold or fungus: poke one of the domes (if they are domes) with a stick or something. A scale insect will be squished like any other bug.
Unfortunately, if it is scale, then there isn't much you can do, but you should move all potted plants away to prevent the scale from spreading. They are extremely hard to get rid of. It usually involves spot treatment with ethanol or manual removal on a small plant, and then you have to do it ever day to ensure no offspring mature. For larger plants, the most common treatment is removal... I recently removed scale from a plant simply by cutting off all the branches and letting them grow back in, but I don't think a magnolia would survive that.
Anyway, check if it is scale before attempting treatment or removal.
Would an oil spray work to smother out the scales?
That may work, but I'm not sure. Whatever treatment you do, you will have to repeat every couple of days for quite a while, otherwise eggs will hatch, mature, and so on. Here's a pretty good info site:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
