How to Control Scale Insects on Texas Mountain Laurel

Q. I planted a Sephora secundiflora in my backyard about 17 years ago. Today, I noticed many of the stems are infested with an insect that looks like a type of scale to me. The stems and leaves below the infested stems look wet and sticky.  The pavers underneath the plant are also wet and sticky. 

Those small red bumps on the branches of Texas Mountain Laurel, Sophora secundiflora, are insects

A. Your picture helped tremendously. 

Those red bumps are scale insects

Yes, you are correct. These brown, round bumps on the stems are scale insects. I have never seen these on Sophora, Texas Mount Laurel, before and I could find no reports of scale insects on this tree from anywhere. Scale insects provide a food for ant colonies, as do aphids. It’s mostly sugar from plant sap. That’s the sticky wetness you are seeing. Ants have a vested interest in protecting and colonizing ant and scale populations because of this sugary, sticky wetness.

Horticultural oils are pesticides made, typically, from a refined mineral oil.

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            The most effective control of scale insects are repeat stem sprays of horticultural oils. These sprays should be applied several times during the cooler times of the growing season. Combine this spray with ant control in the same area.

Aphids and ants on apricot in Tajikistan

            Ants move scale insects around, much like they do aphids, to different plant parts and even different plants. They contribute to the spread of scale insects in trees and shrubs and can turn a minor problem into a major problem in a couple of months.

Some Amdro products are ant baits and can be used to kill an ant colony that is spreading and protecting insects producing sugary exudates like scale, aphids and others.

Controlling ants

            When controlling ants, use a poison bait in locations where there are problems. If there are no problems, no control treatment is necessary. Ants play a positive role in protecting plants from other insects.

            An insecticide called Amdro, an ant bait, has been effective in controlling the spread of aphids by controlling ant colonies. I see no reason why this treatment would not also control the spread of scale insects. You can find Amdro ant bait at any garden center or nursery.

            Most of our ants live in the ground in colonies. Identify the soil opening or openings to these ant colonies and spread 15 or 20 granules on top of an ant mound. Ants take this poisonous bait into the underground nest where it kills the entire population in 24 to 48 hours. The area where it’s applied must stay dry for 24 to 48 hours to work. Make sure the label of this product fits the needs at your site before applying it.

When to spray horticultural oil

            Horticultural oils are sprayed over the entire tree, top to bottom, if temperatures are below 90° F and no flowers are present. Repeating this spray three or four times during the growing season provides nearly 100% control of scale insects.

Follow-up with soap and water sprays

            Apply soap and water sprays to the tree 7 to 10 days after the horticultural oil application. Soap and water sprays kill any young nymphs that eluded the oil application. Remember, soap and water sprays, just like oil applications kill all insects sprayed, good or bad. Direct soap and water and oil sprays only to locations where there are problems.