May 31, 2012

Here's Randy's Weekly KTRH GardenLine Tip:

Issue #260

Lately, I've been overwhelmed with questions about crape myrtles. So, I don't think there could be a better topic for this week's tip sheet, and I've put together a re-issue of what I've previously referred to as "The Crape Myrtle Chronicles."

I was also prompted to re-work these tips by my expectation of how bad insect problems will be for crapes this summer. Since we didn't have a normal winter, and since 90-degree days are already here in May, you can actually believe the insecticide advertising you've been hearing on the radio predicting that we could be in for a major insect explosion.

But, you can be somewhat proactive. For example, to prevent an infestation of aphids and whiteflies this summer, treat periodically with a liquid insecticide. Or feed and treat with a systemic insecticide and systemic food. Almost any liquid insecticide will work in the prevention stage, but the one insecticide I would NEVER advise using on crapes is malathion. It will likely defoliate the tree.

If you've already seen a shiny gleam to the leaves, that is a sign that you're already in the early stages of an insect problem. This is when you spray with any number of insecticides, with bifenthrin being the first, best choice. Other active ingredients that are fair game for crapes are sevin, permethrin, deltamethrin and lambda cylothrin. In most aphid cases (right), one spray with a synthetic product should do the trick. With organics, however, you will have to be more vigilant and spray every week for a month to overcome early infestations. You can see success with spinosad and even neem oil. Be careful with homemade, "organic" formulas, though, because a little too much of this or little too much of that can burn crape leaves in this heat.

So, here are the tip sheets I've published over the years concerning crape myrtles ... from controlling black sooty mold and white powdery mildew, to prolonging the bloom season, to simple care practices that help prevent these issues in future.

BLACK SOOTY MOLD - INSECT INFESTATIONS
If you've already seen an outbreak of black sooty mold (left), you're no longer in the preventative stage.

WHITE POWDERY MILDEW
The next most often asked crapes question at this time of the year has to do with this fungal-type subject ... the white film (below right) that seems to dust the leaves right after wet, humid, cooler-than-normal nights.

PROLONGING THE BLOOMING SEASON
Many folks want to know how to prolong the blooming season on these wonderfully colorful landscape specimens. Here are the tricks.

CRAPE MYRTLE FLOWER FAILURE
Here's a tip sheet about the unusual flower-failure seen by some crapes. If we get excessive rains, the problem may begin showing up.

AVOID BEING PART OF THE ANNUAL CRAPE MYRTLE MASSACRE
Finally, this tip sheet has to do with the crape myrtle massacre or crape murder that takes place every year. I included a letter in the introduction to my new book from Debbie Johns who moved here three years ago from Michigan. She followed the advice of some uninformed or uneducated landscaper and over-pruned her crapes each year to the same spot. Then, she started listening to me and followed the tips here. Now her crapes are beautiful.

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