Wednesday, September 02, 2009
Saving bleached-out azaleas
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
Or send an e-mail. Answers will be given only in this column. Please don't send pictures or samples.
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Q: It looks like I have a problem on some of my azaleas. The leaves have lost their good green color and look like they have been splashed with droplets of bleach. Not all my azaleas look this way. What could be the problem? I recall that some of my azaleas got this speckled appearance last year. I did nothing then, and the problem is recurring. I live in the upper part of the South.
A: It sounds like your azaleas thave been damaged by the sucking of an insect called the azalea lace bug. This pest especially likes azaleas planted where they get direct sunshine.
Turn the injured leaves over and you likely will see the pests and/or signs that they have been there. Clues are little brown dots of the excrement that azalea lace bugs leave on the underside of the foliage that they have been feeding on.
In Roanoke, azalea lace bugs might be present during late summer, but control might not be practical at this time. They are better controlled on azaleas after mid to late May when the bugs' eggs hatch.
Control applications must be repeated at three-week intervals. I have had good success using the insecticide called Orthene. Killing azalea lace bugs is difficult because these pests do their damage on the lower side of the leaves, making adequate spraying difficult. Contact your local office of the Cooperative Extension for legal recommendations in your state.
These bugs pierce the leaf and then suckplant sap through their slender mouth parts. These pests are about 1/8- to 1/4-inch long and get their name from their delicate lacelike appearance of their wings and body surface.
Still, your azeleas may have not been injured severely. Heavy damage to azalea leaves shows up as silvery, coppery, or even browning of entire leaves as spots come together -- usually when azaleas are in a sunny part of the landscape.
Q: Can you tell me if the Heritage variety of river birch is supposed to make dense shade after several years of growth? I am growing this delightful variety of birch where I can enjoy the clump of trunks with their light-colored peeling bark in my landscape. The birch is about 20 or 25 feet away from some tall maples or oaks and it is not very dense, like I think it should be. Please help.
A: The river birch does not provide dense shade like a well-branched maple. The closeness of your maples or oaks is probably preventing your birch from being as dense as it should be.
One advantage of the landscape placement of your multi-trunked birch is that you can more easily enjoy the sight of its bark. If you want it to provide more shade, you’ll likely have to thin out some of the nearby trees. Fertilizing the birch will not make it denser.
