Crape Myrtle Pest and a Bigger Issue

 Dirt Doctor Organic News #14

There is a big push to plant crape myrtles in the city of McKinney, Texas these days, and in other cities as well. They are beautiful trees and unless they are overused, they will be an asset to the landscape.

The landscape industry is finally helping by stopping the cutting back of the tops of crape myrtles in the winter. This tree butchery is a silly waste of time (same goes for other trees) and it is actually bad for the flower production. It should go without saying that the structure of the tree is ruined by cutting back the trees. Even the seed pods should be left. They are decorative and the seeds feed the small birds.

The new pest (if it’s been around before, I missed it) is the Florida wax scale.

Florida wax scale young and adults

Common Name: Florida Wax Scale (Ceroplastes floridensis).

Common Hosts: Crape myrtle, deodar cedar, elms, hollies, loblolly pine, oaks and other hardwoods and softwoods.

Description: The adult is approximately 3 mm wide; circular, raised, dirty white to pinkish with a wax cover. The nymphs are smaller and star shaped.

Importance: Severe infestations may result in shoot or branch dieback.

Signs of Infestation: Foliage discoloration and shoot dieback. Soft waxy domes adhering to leaves, shoots and trunks. Sooty mold is often present as well.

Control: Promote tree vigor and health. Use an approved organic insecticide for infested trees. Best choices would include horticultural oil, fire ant drench and spinosad. Apply the Sick Tree Treatment for long term control.

Soft Wax Scale: (Ceroplastes destructor)is a similar pest.

This scale attack has apparently been fairly common, but I had trouble finding an example. Finally, I found one and guess what - the tree was too deep in the ground, partially because of the flower bed built under it. The scale can be killed with most of the organic pest control products, but getting the root flare exposed is the real solution.

Here is the cause of the insect attacks. The root flare is completely buried.

The other crape myrtle problem (bigger by far) requires looking down. Almost all newly planted crape myrtles, like this one I found, are planted too deep in the ground They need to be planted with the root flare above the ground. If it’s too late, the soil should be removed with the air spade. Homeowners can do the work, if they are very careful, with gently running water and a shop vac. A stiff brush will also work.

This is what the flare should look like on a crape myrtle.

Here is the basic information on crape myrtle from my Texas Trees Book.

Naturally yours,

Howard Garrett
The Dirt Doctor

QUESTION: We have five large crape myrtles that are about 10 years old. Four have purple flowers, and the largest has white flowers. We recently noticed that where the white tree has been trimmed over the years there are small, egglike, white Styrofoam-looking capsules on the bark. When we mash these white capsules, they turn purple. We’ve also noticed small ants on the tree.  M.N., Dallas

ANSWER: The ants aren’t a problem. The capsules are scale insects, which can be killed by spraying a solution made with 2 ounces of orange oil and 1 ounce of  Bio Wash (www.soilmender.com) per gallon of water.

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