Identification
Scale insects are small, sap-sucking pests that appear as immobile bumps on plant stems, leaves, or fruit. They range in size from 1 to 5 mm and can be round, oval, or elongated. Their colors vary from brown, gray, and yellow to white, depending on the species. Scale insects have six legs in their early nymph stages but lose mobility as they mature and develop protective wax coatings. They are commonly found in warm, temperate regions worldwide.
Lifecycle & Reproduction
Scale insects undergo incomplete metamorphosis. Females lay eggs under their protective covering, which hatch into mobile crawlers. These crawlers disperse and settle on plant surfaces, where they molt into sessile nymphs. Adult females remain immobile, while males develop wings and live briefly to mate. Some species reproduce asexually. Multiple generations can occur annually in favorable climates.
Habits, Diet & Behavior
Scale insects use piercing-sucking mouthparts to extract sap from plants, weakening them over time. They prefer woody plants, fruit trees, ornamentals, and greenhouse plants. Most species remain stationary after settling. Soft scales excrete honeydew, leading to sooty mold growth, while armored scales do not produce honeydew.
Where You’ll Find Them / Typical Locations
Scale insects infest plant stems, leaves, branches, and sometimes fruit. They are common in gardens, greenhouses, orchards, and landscapes. Infestations are often found on citrus trees, roses, succulents, and indoor houseplants.
Threats & Danger
Scale insects cause plant stress by reducing sap flow, leading to yellowing leaves, leaf drop, stunted growth, and dieback. Heavy infestations can kill young plants or weaken mature ones. The honeydew secreted by soft scales promotes fungal infections and attracts ants, which protect the pests.
Prevention
- Regularly inspect plants for early signs of infestation.
- Prune and dispose of infested plant parts.
- Encourage natural predators like ladybugs and parasitic wasps.
- Avoid excessive fertilization, which encourages soft scale outbreaks.
- Maintain plant health through proper watering and soil management.
Signs of Infestation
- Small, raised bumps on stems, leaves, or fruit.
- Yellowing, curling, or dropping leaves.
- Sticky honeydew residue leading to black sooty mold.
- Presence of ants tending to scale colonies.
- Declining plant health despite adequate care.
How to Get Rid of It
- Scrape off scale insects manually using a soft brush or cloth.
- Apply insecticidal soap or neem oil to suffocate crawlers.
- Introduce natural enemies like lacewings and predatory beetles.
- Use horticultural oils to smother eggs and nymphs.
- Apply systemic insecticides for severe infestations.