Dear Neil: Something is attacking my angel's trumpet (brugmansia). You can see the white insects that are stuck to its leaves, and there are small, black insects there, too. How can I control them?

Answer: The white pests are scale insects. These adhere to leaf and stem tissues and suck the life out of their host plants. Control them with a systemic insecticide such as Merit or acephate.

I didn't see the black insects on your sample. They probably are not doing as much damage, and the insecticide will probably control them anyway.

Q: We'd appreciate your help with our St. Augustine lawn. Light-green areas have appeared on one end of the lawn the past couple of summers even though we have used a quality lawn food followed by a well-known liquid fertilizer. One area remains pale.

A: Odds are your lawn has developed a gray leaf-spot problem. That's a fungal disease that hits in summer. Affected leaves (and often runners) will have diamond-shaped and BB-sized gray-brown lesions on their midribs.

Fungicides will slow the disease, and you must avoid nitrogen fertilizers in the summer.

Fertilize the grass April 1 and repeat it June 1. Then don't feed again until mid-September.

Q: About 10 years ago, my husband brought East Texas cane into our landscape. It has grown invasively, coming up in places where I don't want it. I've tried RoundUp sprays at full strength after we cut it back, but two months later, it returns. How can we eliminate it?

A: Assuming you have the true cane (1-inch-wide leaves), you should be able to kill it with a glyphosate product such as RoundUp.

Spray when the growth is 3 to 4 feet tall, not right after you cut it.

Be sure the spray coats the leaves, and protect desirable plants nearby from any drift that might hit their leaves.

Do not use the material at full strength unless it's a ready-to-use formulation. Using a weedkiller at a very strong ratio sometimes can burn foliage without killing the entire plant, as you wish to.

You can also dig cane out with a sharpshooter spade. To do that, wait until the soil is saturated after a rain.

Q: We have a Shumard red oak (see photos) planted about four years ago. It has had full, even foliage until this year. Can you tell from these photos what might have caused many branches to have only tufts of leaves at the ends?

A: The cause is probably farther down in the main trunk. Usually when I've seen this kind of damage, it's caused by decay or borers. It often shows up three or four years after planting, often because a tree's trunk was not protected with paper tree wrap from the time it was planted.

Red oaks and Chinese pistachios are especially vulnerable to sunscald because they have minimal bark protection. You probably need to get a certified arborist to see the tree.

Q: Why are so many leaves dropping from my fruitless mulberries? Is it iron deficiency?

A: Large-leafed trees start shedding leaves by mid-summer each year. That's especially noticeable when it first turns hot and dry for several weeks.

It is definitely not iron deficiency. Plants that lack iron have yellowed leaves with dark green veins, and the yellowing is most pronounced at the ends of the branches. The affected leaves don't fall off.

The best remedy for your problem: Water deeply.

• If you'd like Neil Sperry's help with a plant question, drop him a note in care of The Eagle, P.O. Box 3000, Bryan, Texas 77805. Or e-mail him at mailbag@sperrygardens.com.

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