Crape Myrtle Fungus?

[VAFisher]

I'm hoping someone can tell me what's going on here. I started noticing this around the beginning of July when it really started to get hot and humid around here. Leaves are turning yellow or red, sometimes with black spots or streaks and will eventually fall from the tree. The trees are still growing strong and the leaves that fall are replaced in pretty short order. But then the new leaves will become affected as well. It's happening to some extent on all of my crapes, both standard and dwarf varieties, but some trees are worse than others.

They are in full sun for about 8 hours per day and are in a mix containing calcined clay, pine bark and pumice. At first, I thought they were getting too dry during the day while I'm gone but I'm not sure that's the case.

On to the pics. Oh, the leaves are wet in the pics because it rained last night. When I water, I only water the pots, except for a week in early June when I was away. They got watered from overhead by a lawn sprinkler and stayed pretty wet for the whole week. I guess it wasn't long after that I started noticing this.

 

[Mellow Mullet]

I see the same thing on my dwarfs. It seems to happen more when the temps really get up (July, August). I think it is just heat related and maybe something that the dwarfs do. Happens every year but the trees seem ok otherwise.

 

[aml1014]

I've noticed this on the crapes at my work.
My first thought was the inner foliage was being shaded to much, but have since learned that it was heat stress caused by our brutal ass sun!
The dwarfs do seem to have it worse, I think @Mellow Mullet is correct that it's heat related, at least it is in my situation.

Aaron

 

[Paradox]

I haven't noticed a problem with my crepe myrtle. Maybe because I keep it where it gets afternoon shade?

 

[VAFisher]

Thanks everyone. The consensus seems to be that it's heat or water related as opposed to fungal. I think next year, I'm going to try a more water retentive mix to see if that helps.

 

[GrimLore]

They are in full sun for about 8 hours per day

Mine stay out in full late morning to evening Sun, I don't have anything that looks like that leaf condition but I use this at the surface of them and I am pretty confident it stops a lot of problems -



Grimmy

 

[VAFisher]

Thanks Grimmy. I could give that product a try but, I'm pretty sure it's not insect related. They all got an application of a systemic insecticide early on this year as a preventative for aphids, which were bad last year. This year, I haven't seen the 1st aphid and I'm still finding dead Japanese beetles on my benches some mornings (earlier this year it looked like a Japanese beetle massacre). So I know the insecticide is still working. They get fertilized once per week with a Grow More product that Smoke recommended in one of the fertilizer threads. So the only thing left would be fungal - or the heat. I'm still leaning towards heat stress and the trees getting a little too dry between waterings.

 

[Eric Group]

Kind of looks like black spot. Grimy' recommended application would knock it out. (Or some sort of spray like Neem oil)
The heat stress in my experience is more of a wilt that leaves the leaves looking thin and dull in color, sometimes the leaves turn yellow or red with brown sections and drop off. Those black spots look like a mildew or something to me. I used to get it on many of mine, and after spraying with Neem oil it would go away.

 

[Stan Kengai]

Crapes are very vigorous and this damage is nothing to worry about. However, they are susceptible to both black spot and powdery mildew. Try using a winter antifungal preventative regimen. @markyscott has a good thread on one. It's amazing how much difference it makes.