The scale insect or barnacle insect (some species of Hemiptera) is a small insect measuring about 30 mm long, oval in shape and flattened. Scale insects belong to the “true insect” family such as bed bugs. These pests can be very damaging to the garden. So, it would be nice if you know how to get rid of it.
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Method 1 of 4: Recognizing Scale Insects and the Damage They Cause
Step 1. Look for adult scale insects
Insect scales are usually white, tan, or brown, but can also be of other colors. Most have a smooth, flat shell, but some look like cotton or downy hair. Adult insects do not like to move.
Step 2. Identify the young insects
Young scale insects have legs and move very slowly-or in the wind-to a point on the plant they like. The color of young insects is often not the same as that of adults. For example, the adult cotton cushion scales (Icerya purchasi) are pale white in color, but the young insects are orange.
After gaining a place, the young insects will attach themselves to the leaves or stems and eventually the legs will disappear
Step 3. Identify what scale insects do to plants
When attached to the plant, the scale insect plugs its mouth and sucks up the liquid.
Scale insects can be a problem for planters around the world. Scale insects can survive the winter on leaves and stems and reproduce when the weather is warm again to suck food from plants in the garden
Step 4. Watch for signs of scale insect damage
The first symptom is yellowish and falling leaves. Eventually the twig and all the branches will die and the tree bark will crack and release sap. Soft scale insect species can damage plants, but the damage is not severe enough to cause the plant to die. The worst problem they cause is honeydew, which is a clear, sticky secretion they leave behind when they eat.
- Aphids-which are small, soft-bodied insects-also secrete honeydew. Aphids are usually green or red in color-though they can be any color, and are more mobile than scale insects.
- Sooty mold, a type of black fungus, often grows on honeydew, causing unsightly black spots on leaves and interfering with the plant's ability to absorb sunlight.
Method 2 of 4: Getting Rid of Scale Insects on Ornamental Plants
Step 1. Scrub insect scales from plants
Scale insects can attack ornamental plants even if they are never placed outdoors. Insects are often invisible while the plant is still in the greenhouse or store where you originally bought it, then thrive when you bring it home. Remove scale insects from ornamental plants by scrubbing them with an old toothbrush, thumb, or cotton swab dipped in isopropyl alcohol.
Step 2. Use insecticidal soap
Insecticidal soap can also be sprayed onto ornamental plants to kill scale insects. Mix about 5 tablespoons of insecticidal soap or very mild dish soap into 4 liters of water.
Pour the soap into a spray bottle and spray the plant-including the undersides of the leaves and stems-until the soap solution begins to drip. Repeat spraying every 4-7 days until the scale insects are gone
Step 3. Don't use regular soap
Do not use laundry detergent, machine dish soap, or dish soap that is highly concentrated and contains additives or antibacterial agents. Soaps like this can damage the leaves and cause discoloration and damage to the leaf tissue.
Method 3 of 4: Getting Rid of Scale Insects from the Garden
Step 1. Use the same method as used on ornamental plants to eradicate scale insects in small quantities
Scale insects generally live outdoors and can attack all species of trees, shrubs, perennial plants (evergreen), even seasonal plants. If the size of the plant is small and the attack is not too severe, just kill it in the same way as for indoor houseplants.
- Scrub the scale insects with your fingernail or an old toothbrush.
- Spray plants with insecticidal soap every 4 days.
Step 2. Prune the plant parts that are attacked by scale insects
When the attack is severe enough, use sharp pruning shears or shears of large cuttings to cut off the most infested branches and leaves.
- Make a cut about 0.5 cm above the leaf or at the base of the branch.
- Use a garden hose and spray the cuttings before applying to other plants to remove any scales that may still be attached.
Step 3. Spray the plants with horticultural oil
This oil is also called summer oil or dormant oil and is useful for killing any remaining scale insects. Spray the oil on the tops and bottoms of the leaves, as well as on the stems. There are a variety of horticultural oil formulas on the market that are just as good. Generally 2-4 teaspoons of oil can be mixed with 4 liters of water, but this size can vary.
Read and follow the instructions for use carefully. Shake the spray bottle vigorously to mix it all up at first, then shake it again every few minutes while spraying to keep the oil mixed with the water
Step 4. Pay attention to the season when spraying
Spray the plants in early spring to kill any scale insects that survived the winter before the plant growth period begins. In the summer, spray the plants in June, July, and August, but only when the scale insects return after spraying in early spring.
Horticultural oil works by making insect scales run out of air when sprayed. This wash may have to be repeated after a week or two
Method 4 of 4: Preventing with Horticultural Oil
Step 1. Test and spray the oil on 1-2 leaves, wait 24-36 hours to make sure the plant is not sensitive to horticultural oil
Some plants, such as juniper, cedar and Japanese maple can be damaged by oil.
If there is no bleaching or yellowing of the tested leaves, go ahead and spray the entire plant
Step 2. Do not spray on windy days
Do not spray plants with horticultural oil when it is windy because the oil can drip on other plants that do not need to be sprayed and damage them.
Step 3. Do not spray the plant when the leaves are wet
The oil will not stick well to the plant and may wash away before it kills the scale insects.
Step 4. Do not spray oil on a humid day
When the relative humidity reaches 90% or more, horticultural oil should not be sprayed on the plants as it will not evaporate quickly enough. If the temperature is more than 38 °C, the plant can be damaged.
On the other hand, if the temperature is below 4 °C, the oil will not cover the entire surface evenly and this will make the spraying ineffective
Step 5. Do not spray oil on certain plants
Leaves on plants that are stressed or withered due to lack of water will be more easily damaged when sprayed with horticultural oil. Other than that:
- Do not spray the oil on new or young plant stems or leaves as this can damage them.
- Plants that have been treated with sulfur for fungal diseases 30 days earlier should not be sprayed with horticultural oil. The oil can cause a plant-damaging reaction when it comes into contact with sulfur.
Step 6. Wear protective goggles when spraying oil
Horticultural oils are not particularly toxic to humans or animals, but can irritate the eyes and skin.
