How to get rid of scale insects

The complete guide

Scale insect

Difficulty High

Frequency High

Reproductive rate Up to 250x

Lifecycle Up to 60 days

Scale insects, also known as scales, are small plant pests protected by a hard shell that attach themselves to plants to feed on their sap. Their presence can severely weaken the plants and lead to reduced growth.

Houseplants

Fruit trees

Identifying scale insects

Scales are mostly immobile, and their appearance varies greatly depending on thousands of species. As a result, they can easily go unnoticed until a close inspection is carried out. These pests produce honeydew, a sticky substance visible on the leaves.

Early infestation

Presence of a few scales
Sticky substance on leaves and stems

Advanced infestation

Numerous immobile scales visible
Slowed or stunted growth
Yellowing and leaf drop
Black mold on leaves and stems

Treatment options

Indoor plants

Small greenhouses

You will need :

Scissors / Pruners
Plastic bags

Natural predators :

Green lacewings

How to treat scale insects?

The most effective and safe strategy is to dislodge the majority of scale insects using a strong water jet and introduce green lacewings to detect and eliminate any remaining individuals.

1

Preparation

Removing debris from the soil of a tropical plant

Remove debris

Start by removing dead leaves and other debris from the plant.

Wrap the pot

Wrap the pot in a plastic bag to protect the root ball during the treatment.

2

Cleaning

Prepare a workspace

Prepare a workspace that can get wet; ideally outside, in the sink or in the bathtub.

Adjust the water

Use the strongest jet of water possible without damaging the plant (hose, faucet, showerhead, etc.).

Cleaning a tropical plant with a powerful water jet

Wash the leaves and stems

Generously spray all the leaves and stems, paying close attention to the nodes and small gaps. Cover all angles in several passes.

3

Drying

Let the plant dry

Wait for the leaves to be completely dry before introducing predators.

4

First introduction

Installation of green lacewing strips in the foliage of a tropical plant

Introduce the lacewings

Install the lacewing strips in the plant’s foliage.

5

Second introduction

Repeat the introduction

Wait three weeks and repeat the same introduction.

A few important points

Natural predators are particularly effective at detecting hidden scale insects once their population has been reduced. The more thorough the initial cleaning, the higher the chances of success.
Since adults are particularly resilient and nymphs can remain hidden in the plant’s crevices for some time, multiple introductions are generally necessary.

Once the treatment is complete

Inspect the plants regularly for at least eight weeks. If new signs of scale insects appear, repeat the cleaning of affected plants every five days. Otherwise, you can consider your treatment successful. For added caution, feel free to carry out a few additional introductions of green lacewings.

Do I absolutely need to treat all my plants?

Armored scale insects spread quickly, and the absence of symptoms does not mean the plants are healthy. It is therefore strongly recommended to treat all visibly affected plants as well as those nearby.

What should I do if I cannot wash a plant with a water jet?

If washing the plant with a water jet is not possible, it will be very difficult, if not impossible, to treat armored scale insects. Consider discarding the plant or taking cuttings.

Do I need to repeat cleaning before each introduction?

Cleaning is always necessary before the first introduction. If the initial infestation was severe or many insects are still visible at the time of subsequent introductions, it is preferable to carry out another pre-introduction cleaning. Conversely, it is no longer necessary once the infestation appears to be under control.

Is it necessary to replace the substrate to treat armored scale insects?

Nymphs and adult armored scale insects remain on the foliage. Not only is replacing the substrate unnecessary, but it also causes additional stress that could further weaken the plant.