Move Over WPS, There's a New Scale in Town

This year has been so busy for the Champion Tree Health team. Between the scorcher of a summer and the 60+ beech trees we’ve injected to combat beech leaf disease, on top of our regular plant health care visits, we’ve received a surge of calls about a new pest showing up on crepe myrtles in our area.

Over the years, crepe myrtles have become a staple of Main Line landscapes. Their vibrant summer flowers and awesome smooth, peeling bark make them a standout tree for homes, parks, and streetscapes. Even in winter, they add a sculptural element to gardens with their elegant branching and patterned bark. While crepe myrtles aren’t the most low-maintenance or problem-free plants (looking at all the aphid and powdery mildew–ridden trees we’ve treated this year), we now need to add one more ailment to the list: crepe myrtle bark scale (CMBS).

A Little Background: 

Crepe myrtle bark scale (Acanthococcus lagerstroemiae) is native to Asia. It was first found in the U.S. in 2004 near Dallas, Texas (Ask IFAS). Since then, it has spread steadily through the southern United States and is now being reported in mid-Atlantic states, including parts of Pennsylvania.

How did it end up here? Since CMBS cannot fly, the most likely way it reaches new areas is through nursery stock transported from southern states. A crepe myrtle that appears perfectly healthy can actually be carrying hidden eggs or immature scales. Once planted, the pest spreads locally when the crawler stage (the only mobile stage) moves across branches or hitches a ride on wind, birds, insects, or even animals (PSU Extension). In warm southern states, CMBS can complete 3-4 generations a year. Here in southeastern Pennsylvania, we’re expecting 2-3 generations, but this is speculative and still being studied.

What to Look For?

CMBS won’t usually kill a crepe myrtle outright, but it can seriously weaken trees and make them look unsightly: 

• Fewer flowers and weaker overall growth
• Sticky honeydew dripping onto patios, cars, and sidewalks
• Black sooty mold growing on bark and leaves, feeding on honeydew

Clusters of white, fuzzy scales along the bark that stand out on dark branches.

Often, sooty mold is the first clue of an infestation. If you notice your crepe myrtle’s bark or plants underneath turning black and sticky, it’s worth taking a closer look.

Our Game-Plan: 

At Champion Tree, we take a low-impact approach to managing pests. We do not use neonicotinoids pesticides, which are harmful to pollinators and other beneficial insects.

Instead, we plan to combat CMBS using the same strategy we use for white prunicola scale and other pests (Read more about that here): 

• Carefully tracking the pest’s life cycle and local growing degree days
• Timing treatments for when the insect is at the crawler stage (most vulnerable stage)
• Using targeted sprays to disrupt the population without harming the surrounding landscape

This method requires close monitoring and precise timing, but it’s effective and environmentally responsible. By focusing on the crawler stage, we can manage CMBS populations while protecting the larger ecosystem.

A crepe myrtle we sprayed recently, crawlers were observed!

We’re hoping this crepe myrtle bark scale doesn’t become the next white prunicola scale, which has been wreaking havoc on laurels across the Main Line for years. If you notice your crepe myrtles struggling, whether it’s sooty mold, sticky bark, or fewer blooms than usual, give us a call! We can help diagnose the problem and get your trees back to looking gorgeous.