Question
Hello, I saw an older post while looking up crape myrtles. We bought a house with LOTS of mature crape myrtles, but last summer, few blooms. Around February, I pruned them and fertilized them.
This spring, the suckers abounded all over the tree. Lots of new growth. Lots of buds. At first, we got some blooms, but spotty. I saw your older post and I did notice some powdery substance on the leaves. Some leaves are a bit dried looking. I think this might be my problem.
Thanks,
Ed G.

Answer
Mildew is not ONE problem; it's any of SEVERAL problems, triggered by a long list of Fungus villains.  Its signature soft-gray powder coats buds and leaves -- especially new tender growth, halting photosynthesis and other basic life processes, sapping energy, busting buds, wrecking flowers.

Warm, dry days and calm, cool nights plus sky-high humidity prompt growth of stealth Mildew spores that lie in waiting everywhere.  You did not mention your location -- is this weather you had preceding onset of those symptoms?

Oddly, these Fungi only grow on dry leaves.  Daily water-baths limit its advances.  If this sounds like what you're looking at, toss ALL diseased plant material and drench ALL leaves -- over and over -- with the usual Baking Soda-Horticultural Oil formula.  That stuff by the way will work just as effectively as anything you can buy in the store called 'Fungicide' with a skull and bones on the label.  But without the nasty side effects.

Next year, don't stop spraying just because the symptoms have not appeared.  Because now that you have it, you can expect a repeat performance next year as soon as weather permits.  You have to figure at least a couple of spores are going to make it through your gauntlet.  Mark your June '08 calendar and start spraying BEFORE symptoms appear.

Now, although few people realize this, once a Fungus -- ANY Fungus -- establishes itself in your Garden, almost all the time you can bet that the only way to get rid of it is going to be by waiting for it to die of old age.  You have to make sure until that blessed event that NONE of its microscopic progeny EVER inherits the house.  Nothing will really kill most happy, healthy, well heeled Fungus colonies.  Nothing.

That's why you'll see authorities always telling you things like: 'Best control is prevention through a regular program of spraying and dusting with Fungicides from June until frost.'  They're not kidding.  (That advice by the way was lifted off the North Dakota State University website 'Roses' page:
http://www.ag.ndsu.edu/pubs/plantsci/landscap/h118w.htm)

You should know that some Fungicides will trigger a major infestation of Mites.  This happens because the Fungi that attack the Mites are suddenly eliminated.  This is one problem I have with companies like Scotts that act like they're doing us all a big favor by selling us Fungicides.  Like, it's supposed to help.

The problem with Fungicides is that most Fungi are GOOD Fungi.  The whole Fungus Kingdom is a group of critical decomposers and recyclers.  Fungi are mini-catering halls for flowers and trees, delivering special nutrients underground, straight to the roots.  And it doesn't stop with our Garden soil.  Think about it.  Penicillin.  Streptomycin.  Tetracycline.   How many lives have they saved since they were discovered?

You like Truffles in your Salad?  Mushrooms on a Shish Kebab?  Stuffed?  Fungi!

You like Blue Cheese Dressing on that Salad?  Fungi!

You like Bread?  Beer?  Wine?  The Yeasts that make them possible: Fungi!

In the Garden, Fungi are reliable predators of things in our soil that we don't want around.  They compete, control, sometimes even defeat Bad Fungi, or they attack Bad Insects.  So when you wipe out ALL the Fungi in your soil (like Mildew) with a Fungicide, you're on the verge of turning a small headache into a major Migraine.

Back to your Myrtle.

Insects that drain tissue by sucking the life out of leaves and buds -- Aphids, Scale, Whitefly to name a few -- also cause leaves to curl or twist and wilt.  This gets worse as moisture is depleted from the tissue.  Aphids frequently hunt around for a big juicy Crape Myrtle to call home.  Sapped of strength, a Crape Myrtle with an Aphid problem cannot bloom up to par.

But since you bugsprayed -- by the way, Ladybugs are much more effective, and they are totally non-toxic -- we can assume this would have solved the problem if it was Bugs that was your problem.  But PLEASE make a note that if you have Aphids in the future, give the old Ladybug Family a try.  Failing that, give Horticultural Oil a chance; it works by suffocating target insects, and it is as pure Green as it gets.

So let's assume you have a Mildew problem.

When Powdery Mildew strikes leaves, the flowers emerging from infected buds also show signs of Mildew blight.  But there are other things that can weaken the flower power of a Crape Myrtle.  Shade keeps Crape Myrtles from building up enough energy for flower production, and it keeps sprouting Mildew spores comfortable.  A Crape Myrtle needs at least 8 hours of direct Sun to live up to its full flowering potential.

Also, since you inherited this stand of Myrtles, you should also be aware that there are Crape Myrtles that are just not programmed to bloom a lot.  No matter how much love you give them, without the right DNA, they just won't ever look as good as one with the right genes.  Consider that possibility if you have not witnessed a big flower show from this stand.

Like any flowering shrub or perennial, a Crape Myrtle needs to get adequate vitamins and minerals for flower production.  When new wood is destroyed over the winter by cold weather, or removed while pruning, you often see fewer flowers.  Too much fertilizing can also ruin your flowering plants.  Since you have not been dealing with a lack of buds, it would surprise me if this was the problem with your Myrtles.

Dave Beaulieu's About.com page on Crape Myrtles points out:  'pruning out branches that cross over other branches (thinning) promotes air flow and reduces susceptibility to Mildew.'

You can read his whole column here:
http://landscaping.about.com/cs/shrubsbushes/p/crape_myrtles.htm

All this said, it certainly does sound like you are dealing with a Fungus attack.  BAD Fungus.  Make your move and see what you can pull off to fix it.  Any questions on this, let me know.  Thanks for writing.