How do I permanently eliminate scale insects?
Written by
Benjamin Miller
Reviewed by
Prof. Martin Thorne, Ph.D.For the complete eradication of these scale insects, it is essential to understand their life cycle and their weaknesses. These insects live under a protective shell and are thus difficult for you to attack. I have found that using both physical methods of treatment and biological controls has yielded success in the greenhouse. You must eliminate their breeding, but you must also protect the beneficial insects.
Initial Manual Removal
- Scrub visible scales with alcohol dipped cotton swabs
- Focus on stem joints and leaf undersides
- Rinse plants to remove dislodged insects
Oil Spray Application
- Use neem or horticultural oil at dusk
- Cover all plant surfaces thoroughly
- Repeat every 7 days for 3 weeks
Biological Control Introduction
- Release ladybugs at night above 50°F
- Apply scale targeting nematodes to soil
- Avoid chemicals for 8 weeks prior
Systemic Treatment For Severe Cases
- Use soil drench insecticides sparingly
- Apply only during non flowering periods
- Wait 8 weeks before harvest
Preventative Maintenance
- Inspect plants weekly with magnification
- Quarantine new plants for 3 weeks
- Wipe leaves monthly with soap solution
The appropriate season is crucial for controlling permanent scales. Direct your attack in spring at the crawler stage, when the young scales are moving between hosts. Apply treatments at chilly times of day to avoid burning the leaves. I have my greenhouse treatments made at sundown when the temperatures fall below 80° F., so that the effectiveness is greatest.
Environmental protection is important throughout treatment. Always try sprays on individual leaves first. Protect pollinators by working only outside of flowering periods. Wear gloves when handling the materials. My hibiscus survived because I alternated between hand-picking and biological controls.
Consistency makes extermination permanent. Keep watching for 8 weeks after you stop seeing visible scales. Use sticky traps in your plant to capture errant crawlers. Remember that scale eggs have wave hatching patterns requiring multiple treatments. My battle against the citrus scale took three perfectly timed applications of neem oil.
Read the full article: Scale Insect Treatment Methods Explained
