Scale insects are a varied group of soft-bodied insects that are known for their domed scales and waxy deposits that serve as a protectant. Most scale none are directly harmful to humans but may cause an allergic response in some people.
The Coccoidea family of insects has been used by humans since antiquity as a source of dyes and varnishes and are a very uncommon pest. They are generally considered to be common plant pests, and the main way they benignly cause harm.
In This Article: We will explain everything you need to know about scale insects, how to control them properly if they are affecting your plants and eliminate them and return..
What Are Scale insects?
With over 8,000 species and sub-species, it can be difficult to explain exactly what scale insects are.
However, there are some features that this family of insects have in common:
- Scale insects are quite small, usually just a few millimetres in length.
- There is a pronounced sexual dimorphism, the female is soft bodied, lacks wings, lacks obvious limbs while the male has wings and legs.
- Generally, females live longer than males, females’ bodies are absorbed into the plant, feeding, while the males die within a couple of days after emergence.
- Scale insects are called scale insects for the domed scale, which females live under.
- As adults, they produce abundant powdery wax.
- They are also related to the mealybug.
- They suck sap and consume and excrete huge amounts.
- Honeydew is the excretion that attracts ants and causes plant disease.
Are Scale Insects Harmful to Humans?
Scale insects are not harmful, as they are not poisonous and do not bite. There is almost nothing that scale insects can harm humans.
Our species has been manipulating and even domesticating scale insects for thousands of years.
Some scale insects, such as cochineal, kermes, and lac insects, produce bright red dyes that are used in many products, including food.
Lac insects are also harvested for shellac, a resin that is used for glazing wood products and can be used to coat food.
At worst, the insects and organic products they produce may cause allergies in certain susceptible individuals with high exposure levels.
Because of Their Feeding, Scale Insects Are a Common Garden Pest
At least 25 scale insect species can be found in the UK.
Due to variations in preferred hosts and life cycles, it is possible for scale insects to affect a number of plants at different times throughout the year.
Their damaging effects on plants can be particularly painful for gardeners and growers that grow plants indoors, in greenhouses or undercover.
How Scale Insects Feed
Scale insects have mouthparts that are formed to pierce the outer layers of a plant and suck its sap.
This is primarily the activities of females who stay attached to the plant.
As the plant juices flow into the scale insect under pressure, the scale insect excrete honeydew, a sweet sugary waste, as waste.
Less-known Fact: This sweet substance is commonly eaten by ants who have a mutually beneficial association with the scale insects, by protecting them from predation.
The Feeding Process of the Scale Insect Can Damage or Kill Plants
Scale insect infestation and feeding on a plant will harm it in 3 ways:
- Reduced Growth because of Parasitism: Scale insects are parasites that rob a growing plant of the nutrients and minerals that it needs. This causes affected plants to drop in height and leaves, and in some cases die.
- Introduction of diseases: Because scale insects penetrate a plant’s outer defenses, disease can be introduced. Weakened by the continued feeding of scale insects, they are therefore, vulnerable to a host of diseases.
- Honeydew induces mould: The honeydew secreted by scale insects promotes black powdery mould on plants attacked by scale insects. This is known as sooty mould.
Signs of a Scale Insect Infestation on Your Plants
If you are concerned about the poor condition of your greenhouse or garden plants and are looking for a cause, the following signs could indicate that scale insects are the culprits:
- examples of distinctive features
- stunted or yellowing plants
- shell-like or scaly bumps on the underside of leaves, between the leaves and on stems with a waxy, varnished coating, usually brown, yellow or white
- you can see small, visible eggs coated by a web of waxy white fibres
- sooty mould on surfaces of the leaves
Controlling Scale Insects in Your garden
If you don’t want to be completely overrun in your garden or greenhouse you need to make sure you deal with a scale insect infestation quickly.
After a prompt response to control a scale insect infestation, it is equally important to prevent future infestations.
Here are the main actions to take.
Organic Control Methods for Scale Insects
- Scale insects can be removed from plants physically. It is also possible to kill or weaken scale insects by repeatedly treating the insect topically with steam or rubbing alcohol.
- There are also organic means of directly assaulting scale insects through predatory insects (ladybird and parasitic wasps), and birds may also take out a fair number of scale insects. An alternative biological control is the nematode steinernema feltiae.
Pesticide Control of Scale Insects
Pesticides should only be used with caution because there is potential for damage to beneficial insects in your garden.
There are a variety of organic pesticides available which can include:
- Plant oil winter wash
- Pyrethrum
- Fatty acids
- Plant essential oils
These can be sprayed on, and are really effective applied in mid-to-late summer, as the scale nymphs have much less physical protection.
Using a pesticide to treat your scale insect issues also will not get rid of the scale insects, once they are dead the remains will remain stuck to your plant.
Have You Observed: The main determinant of their efficacy is whether you notice that the infestation grows larger.
Preventing Scale Insect Infestations
Check susceptible plants regularly for signs of scale insects or their symptoms.
New plants should be examined and quarantined before they are integrated into your garden, greenhouse, or home.
This is good practice to help limit disease in plants. This will improve success to grow healthy and viable plants.
Rounding up
When you think about scale insects, they are wonderful little animals in terms of their usefulness to humans across time.
However, they can appear at the worst time on your wonderful plants.
Although they won’t harm humans, keeping an eye out for them will help ensure that your plants stay healthy.