Yes, you just about have to have sooty mold. It is a mold that grows on the excretions from insects. Any time you see that on any bushes, you should look closer because you have some sort of insect problem. It can be scales, but in this case, it is probably aphids. It is common for large plants even in the wholesale nurseries to get black because of this mold, but it usually happens in another month or two. As others have said, it doesn't kill the plant but it looks ugly. I would spray the plants with something like Malathion, or any other general purpose insecticide to get rid of the aphids. If we had lots of rain, the mold would then wash off in a few weeks. An old remedy is to mix about 4 tablespoons of baking soda per gallon of water, and that is supposed to take out the mold in less than a week.

It's 'black sooty mold' caused by mold growing on the 'honey dew' secreted by aphids. Spraying with insecticidal soap is recommended. The white spots are most likely powdery mildew which some varieties of crape myrtles are subject to mostly in the spring, especially if there is not good air circulation and they are not in full sun. Sometimes trimming out some of the interior foliage will help, plus you can spray them with an anti fungal solution. Good luck. Crape myrtles are beautiful trees and are mostly carefree. Incidentally I find using the Gilmour 362 professional hose end sprayer to be the most convenient way to spray. Amazon.com carries it. Here is a link that might be useful: Google search results for sooty mold on crape myrtles ...

I have 26 Japanese Maples, most purchased as very tiny first or second year plants, and I do no winter protection on them and haven't lost a one in nine years. Get them well established with proper watering this fall, mulch them well, and leave them alone. As far as the Crape Myrtles, in my own experience it depends on how the winter winds move throughout your yard. I will give you a hint on managing them even though it makes me look like an idiot- When I first moved here in '07 I had no idea how to manage many of this zones plants. Spring was an extremely amazing time- I had come from South Florida, so spring was a novelty to me. Every morning I would rush out to look at my new plantings to see buds or leaves. I got busy doing my spring chores- pruning and so on. My first year with Crape Myrtles here (we had them in SoFla as well) they never budded. I always thought the winter had gotten them and pruned them back knowing that the roots had probably survived and they had. They always came back, but seemed to die back every winter. I saw nice big mature Crape Myrtles in my neighborhood, though, and couldn't figure out where I went wrong. Then I had a family emergency year where I had next to no time to garden. I would go out, check the Crape Myrtles for growth and think "I really need to cut those back" but I could never find the time. Finally in about May they budded out! All up and down the stems, too- not just from root growth. That's my very long winded way of saying that they can be VERY late to leaf out. All those years I had cut them back in my early spring frenzy I had been cutting off viable stems. DUH me. I do no winter protection here except for a very few mophead hydrangeas. I try to select good plants for my zone, grow them well, and aside from that they are on their own. I think your plants will be fine.

I am in Australia and have been interested in the chat here. Crepe myrtles thrive here in an arid climate. All around town and in my garden. I have perfect conditions for trees everything grows double the size and twice the rate because I live on 30m of river soil on a flood plain. BUT the dark crepe myrtles are not only falling to thrive but slowing looking worse. We have had two very wet years but the soil has perfect drainage. Everything else in the garden around them is thriving. The common consensus here seems to be they are a weak plant. I might wait a year more and if they don't take off I am going to replace them. Thanks for thoughts everyone.