Bark Scale Treatment
What Is Bark Scale and How Does It Damage Your Plants?
Bark scale is a small, sap-feeding insect that attaches to tree and shrub bark. Female scales are covered with a white, felt-like waxy coating and feed directly on plant tissue, weakening plants over time. Left untreated, infestations reduce flowering quality, cause premature leaf drop, and can lead to long-term decline or death of valuable landscape specimens. Crepe myrtles are especially vulnerable — the crepe myrtle bark scale species evolved specifically to feed on them and has spread widely across the Southeast since its arrival in the U.S. around 2004. If your trees or shrubs are showing black sooty mold, sticky residue, or reduced growth, bark scale may be the cause.
Our Dual-Treatment Approach — Active Season and Dormant Season
Effective bark scale management requires treatment at two points in the year. During the active growing season, we apply Zylam® Liquid Systemic Insecticide as a soil drench, where it is absorbed through the roots and moves through the plant’s vascular system to reach feeding scales from within. During winter dormancy, we apply horticultural oil directly to all bark surfaces, physically smothering overwintering scale populations before spring. Together, these two treatments suppress populations year-round, protect plant health, and reduce the pressure that leads to visible damage. Most customers receive one of each treatment annually, with additional applications for severe infestations.
Active Season Treatment with Zylam®
Our active season treatment uses Zylam® (imidacloprid), a professional-grade systemic insecticide applied as a soil drench around the base of each tree or shrub. The product is absorbed through the roots and translocated throughout the plant, so scale insects feeding on any part of the plant are exposed to the active ingredient. The optimal application window is late March through May, when plants are actively growing and transpiring at peak rates — this maximizes uptake and distribution throughout the canopy. Visible scale decline typically begins within 4 to 6 weeks of application. Soil must be adequately moist for proper root uptake; we will advise you to water 24 to 48 hours before treatment if soil is dry.
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Dormant Season Treatment with Horticultural Oil
During winter, when your trees and shrubs have dropped their leaves, we apply horticultural dormant oil to all bark surfaces — trunk, branches, and twigs — using professional spray equipment. The oil works through physical action rather than chemical toxicity, coating the breathing pores of overwintering scale insects and causing suffocation. Because this treatment targets dormant populations before spring activity begins, it significantly reduces pest pressure going into the growing season. Dormant oil applications are performed December through February and require specific weather conditions: temperatures must be between 40 and 70 degrees Fahrenheit, with no rain or freezing weather forecast within 24 hours.
Fertilization — Supporting Plant Health During Treatment
Bark scale takes a toll on plant health, and healthy plants respond better to treatment and recover faster from damage. When timing and site conditions allow, we coordinate a slow-release granular fertilizer application with your Zylam soil drench during the same visit. This balanced fertilizer provides nitrogen, phosphorus, potassium, and micronutrients tailored for ornamental trees and shrubs. It supports overall plant vigor, improves stress tolerance, and helps optimize systemic insecticide uptake throughout the growing season. For plants recovering from heavy infestations, ongoing fertilization beyond what is included with bark scale treatment may be recommended to support full recovery.
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What's Included in Every Service Visit
Every bark scale service begins with an inspection to assess infestation severity, plant health, and species identification. Trunk diameter is measured for precise product dosing on systemic applications — correct dosing is critical for effectiveness and plant safety. Active season visits include calibrated Zylam soil drench application, fertilization when appropriate, and watering-in if needed. Dormant season visits include full bark spray coverage with professional equipment, ensuring complete coverage of all bark crevices and branch unions where scales concentrate. After every visit, you receive documentation of what was applied and a follow-up consultation. We notify you 24 to 48 hours in advance with specific preparation instructions.
What to Expect — Timeline and Results
Systemic insecticides require 2 to 4 weeks to be absorbed and distributed throughout the plant. Visible scale decline typically occurs within 4 to 6 weeks of application, with complete population reduction taking 8 to 12 weeks. Dormant oil provides faster physical control — scale mortality begins within days of contact. Complete resolution often requires multiple treatments over successive seasons, particularly for heavily infested plants. Most customers achieve 80 to 95 percent population control with a consistent annual program. As scale populations decline, the secondary black sooty mold that grows on scale honeydew will also gradually weather away with rain and new growth — no additional treatment for the mold is usually needed.
What This Program Does — and Doesn't — Cover
This program is specifically designed for bark scale pest control and related plant health support on confirmed susceptible trees and shrubs. It does not include tree pruning, removal, or other arborist services — though we can refer you to a certified arborist for damaged branches that need to be removed. We do not guarantee 100% eradication of bark scale, as reinfestation from neighboring properties and environmental factors are beyond our control. Repair of damage caused by infestations prior to enrollment is also not included. Sooty mold treatment, ant management, and other secondary pest issues are not covered under this program but can be quoted separately.