Scale is an umbrella term used to identify nearly 8,000 species of wingless sucking insects in the order Hemiptera. One of the more common garden pests, these tiny creatures use their tiny straw-like mouthparts to feed on the bark, fruit, and leaves of perennial trees and shrubs.
Different species draw different fluids from plants, ultimately leading to a slow depletion of vital plant nutrients. Affected plants often experience water stress, yellowing of leaves and premature defoliation. Plant parts that are still severely infected may eventually die.
Some species produce a sticky sweet dew, which can further lead to black mold and ant infestations, causing additional damage to the garden. But don’t be too scared – the presence of only a few of these insects won’t threaten the overall health of the plant, and even large populations of some species won’t harm their plant hosts at all.
For example, African blue basil (Ocimum kilimanscharicum x basilicum ‘Dark Opal’) is very resistant to mild pests. In general, mass populations are controlled by beneficial predators and parasites.
However, additional interventions may be required when the natural order is disturbed, such as by ants, dust or persistent use of pesticides. Correct identification of scale families informs appropriate control and possible treatment.
The most common families include armor and soft scales, which can be found in countless plant species. Others are found on various cacti, conifers, elms, oaks, and fig trees. So, how to get rid of scale insects in your garden, read the article below.
Although there are thousands of species of scale insects, about 1,000 of which are found in the United States, life cycles and sex differences are fairly consistent across species.
Adult females and immature nymphs of most species appear plump and wingless, with no distinct body parts. Dense populations produce the appearance of reptile scales on infested plants, hence the name.
Adult males often differ from females in shape, size, and color. They are rare, but are small yellow-and-white insects with a pair of wings and a pair of long antennae.
In some species, males are completely absent, in which case females reproduce asexually.
Various species of the Coccidae and other families, including the cotton pad (Icerya purchasi) and the European elm (Eriococcus spurius), suck the sugar-rich plant phloem sap. As a result, the insects secrete a sticky honeydew – highly sought after by ant populations.
By contrast, armored scales (Diaspididae) and pit scales (Asterolecaniidae) suck on the host’s parenchymal cells, which have little to no fluid and therefore don’t excrete the same tasty residue.
Diaspididae, or species of the Armoridae family, look almost like small barnacles on the outside of an infected plant.
As the nymphs mature, they develop a flat protective shell less than 1/8 inch in diameter.
Insect corpses are beneath this gilded armor. Removing the cover allows the insect body to survive on the plant, albeit unprotected.
Armor scales do not produce honeydew.
Species in this family include cycads (Aulacaspis yasumatsui), euonyms (Unapsis euonymi), oyster shells (Lepidosaphes ulmi), and San Jose (Quadraspidiotus perniciosus) scales.
Soft-scaled species of the family Coccidae are generally larger, rounder, and more raised than armored species. They grow to 1/4 inch long and come in smooth, cotton or wax finish.
Unlike armored species, softscales have no protective shell. If you turn one over, the insects are completely removed from the plant.
The soft scales feed on the plant’s phloem, secreting a sticky honeydew.
The sticky secretion not only drips onto plants and soil, promoting the growth of black mold, but also attracts honeydew-eating ant populations.
Soft scales include black (Saissetia oleae), brown (Coccus hesperidum), kuno (Eulecanium kunoense), lecanium (Parthenolecanium corni), and tulip (Toumeyella liriodendri).
Life cycle of scale insects
These insects hatch from their eggs in spring and summer. They usually mature through two nymph stages or growth stages before reaching adulthood.
Some species change their appearance significantly as they go through these stages, so many types of scales actually appear to develop through more than two growth stages.
The adult female usually lays eggs and then hides them under her body until they hatch, although in some species the eggs hatch inside the female and emerge as live juveniles.
Depending on the species, females can lay anywhere from 50 to 2,000 eggs!
Once the eggs hatch, usually within one to three weeks, the tiny yellow-orange reptile hatches. These are first instar nymphs.
Caterpillars travel across plant surfaces or are transported to other plants by wind, humans or birds. A day or two after hatching, the creeper will calm down and start feeding. This is the beginning of the nymph’s second instar.
Sedentary nymphs can stay in the same place or move slowly throughout adulthood.
For example, soft species that feed on deciduous hosts move from the plant’s leaves to the bark before leaves fall in the fall.
Most types of armor scales have several generations per year.
They typically overwinter as first-instar nymphs or adult females and spend their entire lives in the same foraging site of the plant.
Most types of soft scales have one generation per year.
They usually overwinter as second-instar larvae nymphs. Most immature soft scales retain their tiny appendages and tentacles after weaning and are able to move, albeit slowly.
However, brown soft scales are an exception. It has several generations per year, and both females and nymphs can emerge at any time of the year.
How to get rid of scale insects by organic methods
Pest populations are often controlled by beneficial predators and parasites.
Regularly monitor pest status to observe natural population control.
However, there is also chaos in the natural order of things. If this is the case, you can combine various pest control techniques to make your plants successful.
>>> See more: how to get rid of Leaf miners
Ensuring optimal plant health is essential if you want your plants to survive a dandruff infestation.
When planting and cultivating, make sure your plants get enough sun exposure and watering.
Small, isolated infestations can be easily controlled by selective pruning. Cut severely infected branches and branches and remove them from the site for disposal.
In areas with hot summers, pruning to open the canopy can reduce the population of some species through exposure to heat and parasites.
For plants that prove to be special size targets, you may consider removal and replacement plantings.
For mild infestations, mechanical removal may be the best control option. Use a butter knife to gently scrape off any scale bugs you see.
Rigid hose descent is another control method available.
These techniques require you to carefully remove all insects from your plants; otherwise the infection will persist.
Monitor the plants over the next few weeks and continue to remove until the infestation is completely controlled.
Beneficial insects such as parasitic wasps and certain beetles, lacewings and mites are a gardener’s best friend when it comes to dandruff infestations.
Parasitic wasps, including Aphytis, Coccophagus, Encarsia, and Metaphycus, are the most common natural predators.
These parasitic wasps lay their eggs among the insects. After the wasp eggs hatch, the larvae engulf the insect and expel it through a small hole in the center of the scale’s body.
You can tell if insects are parasitized by the presence of this exit hole. Also, insects do not emit liquid when crushed.
A word of caution – parasitic wasps often have a hard time laying eggs when there are large numbers of ants protecting the scales.
You can find Aphytis melinus parasitic wasps. Additionally, Arbico Organics also supplies green lacewings, and purple scale predators that are also effective.
If you choose to purchase ladybugs for release into the garden, be sure to look for ones that has been raised in captivity rather than those collected from the wild and shipped elsewhere.
How to get rid of scale insects by Organic Pesticides
In addition to mechanical removal, you’ll need a cotton ball soaked in rubbing alcohol to control minor infestations. Alcohol dissolves the waxy protective coating, leaving insects unprotected and vulnerable.
Rub a dampened cotton ball over the surface of the infested plant, making sure you reach each individual.
Or, for a more serious infestation, you can use 1 cup of isopropyl alcohol with 1 quart of water and 1 tablespoon of liquid organic soap (such as Dr. Bronner, Manufacture.
Combine in a spray bottle for a homemade insecticide treatment. Using the flat setting on the hose nozzle, first give the plant a hard spray and knock out as many insects as possible.
Then apply the mixture vigorously, making sure to spray the surface and underside of the leaves.
Repeat the application every few days until the infection clears up.
Not only does this practice kill the pests, but it also helps to flush away any existing honeydew, preventing sooty mold from developing.
Using pesticides should be your last resort. Many can have unintended ecological consequences, so low-toxicity organic pesticides—such as horticultural oils, insecticidal soaps, neem and canola oils—are recommended and may prove effective.
These applications typically have little effect on natural enemy and pollinator populations.
Before applying, double-check your plants to see how much of the population is still active and assess parasitism levels. Wait for spraying when most pests are already infested or dormant.
The best time to apply a foliar spray is during the caterpillar’s life cycle. Since the adult form is coated with a protective waxy substance, most oils will prove ineffective if used at this stage.
Try to apply regularly when plants are not blooming to avoid adverse effects on pollinator populations.
Be sure to read the label on the product you choose to see if the oil is suitable for your plant species. Some oils should not be sprayed in certain ways or mixed with other products.
With oil from a contact spray, the insects are suffocated rather than killed by the poison.
The oil is also effective against aphids, whiteflies and spider mites, but is less harmful to beneficial predatory insects than other insecticides.
Horticultural oils, often referred to as narrow range, premium or highest oils, are specially refined petroleum products.
It’s best to use the spray at least 24 hours before it rains and when temperatures are mild between 45 and 85 degrees Fahrenheit.
Also, they should not be used on plants that are under stress. If drought is an issue, give your plants a healthy drink a few days before oiling.
Spray the affected plant thoroughly with the medication of your choice, making sure to reach the underside of the leaves and the ends of the plant.
Depending on the size and distribution of the population, you may need to apply it multiple times.
How to get rid of scale insects by Chemical Pesticide
Many forms of chemical control can lead to unintended consequences such as: B. Water contamination or poisoning from beneficial predators and pollinators, and can lead to outbreaks of other pests.
A careful study of the type of dandruff can help in choosing a chemical control agent.
Another control option is the use of systemic insecticides. These pesticides are sprayed on part of the plant, usually the stem or roots, and then transferred internally to the leaves and other parts of the plant.
Systemic insecticides offer a control option when temperature limits the use of oil mists.
Plants absorb pesticides into their tissues, which then make their way into the circulatory system and the plant’s sap. When insects feed on the sap, they ingest toxic pesticides and are killed.
The most commonly used systemic insecticides against lime are acephate, dinotefuran and imidacloprid.
Proper identification of the species you are dealing with can inform appropriate treatment.
For example, some insecticides such as imidacloprid are effective at controlling soft scales and other species, but not thyroid or cotton cushion scales. However, dinotefuran controls most species.
A careful study of the details of a dandruff infection will help with treatment.
Do not apply systemic pesticides to plants during flowering. Systemic factors can migrate into flowers and adversely affect natural enemies and pollinators attracted to plant nectar and pollen.
Systems in Check
Not all types of dandruff are considered garden pests.
For example, cochineal scales, commonly found on cacti, are actually sought after by the dye industry for their production of carminic acid, and have recently been revived in cultivation.
Carmine dye is derived from the acidic secretions of insects and is commonly used as a red dye in food, lipstick and textiles.
There are many ways to deal with pests in the garden. Ideally, pest infestations are controlled by their natural enemies.
However, populations of organisms move and evolve very rapidly, and infection may require gardener intervention to ensure plant survival.
Gardeners play an important role in controlling these natural systems.
If you have any questions or further suggestions for using the scale, please let Answer The Question know in the comments section!