GARDENER'S MAILBAG

Control aphids with insecticides, avoid topping crape myrtles

By Neil Sperry | Published Wednesday, February 10, 2016

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Dear Neil: My husband made sure I read your column telling us never to top our crape myrtles. However, ours had aphids last summer, stopped growing and looks terrible. Short of digging it up, can we not just try cutting it down to the roots and letting it start over?

The only time that kind of drastic restart is justified is for a crape myrtle that has been mangled by topping. That way, the new shoots can be encouraged to grow back in their normal growth form.

Aphids are seasonal pests. They coat the leaves in sticky honeydew exudate, and sooty mold then grows in that substrate. The good news is that the sooty mold will be discarded as the old bark sloughs off and is replaced with a fresh covering. You can control aphids in this and future years by applying a systemic insecticide at first signs of their activity.

Dear Neil: Will high-nitrogen fertilizers exacerbate brown patch in St. Augustine in poorly draining soils? Fungicides don’t seem to help.

Poor drainage weakens grass of almost any type. Your St. Augustine would probably develop brown patch almost as rapidly whether you applied nitrogen or not. The type of nitrogen applied, however, will have a direct relationship with the long-term vigor of the grass.

You want a type that has half or more of its nitrogen in high-quality, slow-release form (coated or encapsulated). Watch for first signs of brown patch starting, even in September. When you see the first very faint yellowing in round, two-foot circles, apply your labeled fungicide.

This past year many people didn’t see brown patch until late in the season. By then the grass was reluctant to green up again. They think the fungicide wasn’t working, when in reality, it was just too late in the season to get maximum benefit.

Dear Neil: I planted two dogwoods (one pink and one white) into the perfect soil in my backyard. I have kept them watered well. They look great, but they didn’t bloom this past spring. They were in full bloom when I bought them. What can I do now to get nice flowers this spring?

Be patient. Many of our flowering trees step back away from producing blooms after they are initially planted. They use their moisture and nutrition to produce strong, new vegetative growth. Once they begin to mature in a few years, you can look for more floral bracts. But don’t be too disappointed if they sit another year or two out.

By the way, you can tell right now whether a dogwood will bloom this year simply by looking at the twigs. The buds form in the fall, and they will be very conspicuous over the winter (if they’re there).

Dear Neil: We have two pecan problems. One of our tree’s pecans are all dried up inside. The other tree throws its fruit off way too early. They are black and immature. What can we do to stop these issues?

Hickory shuckworms tunnel around in the shucks of pecans in late summer and cause the kernels not to fill out properly. Control them by spraying with Malathion or other approved insecticides in early August and again in late August. The premature drop of pecans in August and September, especially when they are black and watery, is caused by pecan scab, a fungus. Apply a registered fungicide each time that you spray pecans for other things beginning in early June.

Dear Neil: I’m hoping you can identify this grassy weed and tell me how to get rid of it. It seems to be taking over my St. Augustine lawn.

Without seedheads, it’s a bit difficult to identify grasses, but this certainly looks like rescuegrass to my eye. At any rate, it’s a cool-season grass that germinates in September, then goes to seed by late spring. You prevent grassy weeds by applying Team, Dimension or Halts granules between Aug. 25 and Sept. 7. Water the lawn moderately after you apply them. They form a coat of herbicide that prevents germination of the seeds. Once this weed is up and growing, there is no product to kill it without damaging your St. Augustine. Tolerate it until it dies in late spring, then prevent it in early September and you won’t see it again.

Dear Neil: What is the minimum size of container that a person could use for a Satsuma for all of its life?

They are citrus trees, meaning they can grow rather large (to 15 or 20 feet). It may not be practical to use a pot proportionate to that size. You should be able to get many years out of it if you grow it in a 42- to 48-inch diameter pot. Larger would be better for people who live in warmer parts of Texas where freezes are rare and where the pot could be left outdoors and the plant covered when necessary.

Dear Neil: I saw a story about a shade-tolerant bermudagrass, but I’ve lost the name. What would it be?

Honestly, I am not convinced that any bermudagrass is truly tolerant of less than six to eight hours of hot, direct summer sun. Be wary of claims without seeing the proof. I’ve seen literally thousands of people try all different types over a 45-year career in Texas horticulture, and when the shade gets to those levels, the grass always fails. If a local sod vendor feels that I’m wrong, start with a few square yards on a trial basis. Plant it in April and see how it looks by late June. That would still give you enough time to get more grass planted this year.

Have a question you’d like Neil to consider? Mail it to him in care of the Wise County Messenger, P.O. Box 149, Decatur, TX 76234 or email him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.

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