Many different species of scale insects trouble gardeners. These pests get their name from protective scale-like coverings they produce, which are not part of the pest itself. Scale insects fall into two main categories: armored or soft. As the names suggest, armored scales produce a hard covering, while soft scale coverings are waxy and soft. Both types of scales damage plants, from lawn grasses to shrubs and fruits. Like aphids, soft scales excrete a sticky, sweet substance called honeydew, which attracts nuisance ants as well.
At first glance, many scale insects look like a small, circular bump that's part of the plant. Depending on the species, they vary in color from brown to cottony white and measure up to 1/4 inch long. Scale nymphs are known as crawlers and are similar in appearance. About the size of a pinhead, they're very mobile as they feed. Mature scale insects rarely move once they settle into a spot.
Signs or Damage of Scales
Scales feed on plant juices by piercing and sucking plant leaves, stems and fruits. Adults are visible on plants, though they often blend in. As stem and leaf damage progresses, plants turn yellow, twigs die back and whole plants wither and die. Ant-attracting honeydew produced by soft scales often develops black sooty mold.
How to Control Scales
Effective scale control targets mature pests and immature scale "crawlers" before they develop protective coverings. GardenTech brand offers several products to kill scale insects and protect against scale damage:
- Sevin Insect Killer Ready to Use2 kills scale crawlers on contact. This convenient product is ideal for target spot treatments of specific plants or small garden areas. The adjustable nozzle lets you choose the spray pattern. Just shake the container and you're ready to go.
- Sevin Insect Killer Concentrate provides a simple and economical option to treat scale on small trees and shrubs as well as larger lawn and garden areas. Used with a pump-style sprayer, this product kills by contact and keeps protecting against scales for up to three months.
- Sevin Insect Killer Lawn Granules target scales at ground level, including species such as "ground pearls" that suck sap from grass roots. Apply the ready-to-use granules with a regular lawn spreader, then water immediately to release the active ingredients and reach scales above and below the soil line. This product protects against scales for up to three months.
Scale Control Tip: Ants will protect honeydew-producing scale insects from beneficial predator insects that normally help keep scales in check. Maximize scale control by treating nuisance ants as well.
Always read product labels thoroughly and follow instructions, including guidelines for listed plants and pests, application frequency and pre-harvest intervals (PHI) for edible crops.
GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.
Sevin is a registered trademark of Tessenderlo Kerley, Inc.
- "Scale insect" by USGS Bee Inventory and Monitoring Lab (public domain)
- "Ants tending scale insects on a leaf" by Scot Nelson licensed under CC BY 2.0
- "Citrus Scale" by Scot Nelson licensed under CC BY 2.0
- "Oystershell scale (Lepidosaphes ulmi) (Linnaeus)" by Whitney Cranshaw at Colorado State University (Bugwood.org) licensed under CC BY 3.0 US
- "Tahitian gardenia: Sooty mold and scale insects" by Scot Nelson licensed under CC BY 2.0