Whether you have a dwarf citrus tree or an entire grove, there’s one pest that’s both common and highly destructive: plant scale.
Scale infestations not only harm your tree but can lead to several additional problems. These problems might stunt the tree’s growth, impact production, or even kill the tree in extreme cases.
The good news is there’s a staunch ally willing and able to combat the plant scale menace.
The bad news is that this ally, neem oil, is most often used on smaller plants.
But, can it defend something as large as a citrus tree from the scale insect pests like armored scales and soft scales?
Does Neem Oil Control Citrus Tree Scale?
With the right application method and a little patience, neem oil can protect your citrus tree just as effectively as it protects your garden and houseplants.
Here’s what you need to know about plant scale insects and using neem oil against an infestation.
How Scale Insects Harm Citrus Trees
There are hundreds of species of scale, some of which prefer your citrus trees to other plants.
These tiny insects have piercing mouthparts that puncture the leaves of your tree and extract sap and plant juices.
Their excrement contains partially digested sap, known as honeydew.
This honeydew presents the second threat to your plant.
Ants are attracted to honeydew and will actively protect aphids, scale, and other insects from natural predators in exchange for this food source.
This means the scale colony can expand without natural control methods to keep them in check.
You can create a barrier to help prevent ants from reaching the scale, but an established colony will still require human intervention.
The honeydew is also a prime breeding ground for sooty mold.
Sooty mold will spread across the leaf surface, interfering with photosynthesis.
Over time, this can result in dieback and defoliation.
What Neem Oil Does
Raw neem oil contains at least five natural ingredients known to have insecticidal properties, the most potent is Azadirachtin.
When ingested, Azadirachtin mimics the natural hormones of most insects.
It can cause adult plant scale to stop eating or become infertile.
Meanwhile, it interrupts the development of nymphs, preventing them from reaching adulthood.
Often, the Azadirachtin is extracted for use in other pesticides, leaving behind what’s known as clarified hydrophobic neem oil.
This version has between .5 and 3% percent Azadirachtin and is used as a contact poison.
This form will clog the airways of insects, causing them to suffocate.
Neem Soil Soaks: The First Line of Defense
Neem oil is often applied as a foliar spray on small plants, but this process isn’t practical for something as big as a citrus tree.
Instead, you will want to use a neem soil soak as your primary defense method.
To make the Neem oil soak, mix 1 teaspoon of Dawn dish liquid, pure castile soap, or insecticidal soap in one gallon of water to create an emulsification.
Next, add 2 tablespoons of 100% percent cold-pressed raw neem oil per gallon.
For smaller plants and shrubs, including smaller dwarf citrus trees, you will only need 2 to 4 cups poured directly on the ground around the plant, but larger trees will naturally need more.
It may take some testing to determine the exact amount a particular tree needs based on its size and root spread.
The neem will be absorbed by your tree’s roots, turning into a systemic insecticide.
Any pest that chews on or pierces the plant will ingest the Azadirachtin.
Soil soaks remain within the plant for up to 22 days and reapplied every three weeks as a preventative.
NOTE: It can several weeks for the neem to eliminate an infestation due to the way it kills.
Neem Sprays: The Secondary Defense
Neem foliar sprays have a similar recipe but use clarified hydrophobic neem oil instead, usually at a 1 to 2% percent strength.
These sprays are most effective when used to thoroughly soak every part of a plant, so they’re harder to use and thus less effective the bigger the plant gets.
For a tree spray, mix 2 tablespoons of the clarified neem per gallon of emulsified water.
You will need to spray at either dusk or dawn to avoid harming beneficial insects.
Apply the neem mix using a sprayer and try to be as thorough as possible.
The spray should be reapplied every 7 to 14 days as both a treatment and preventative.
When dealing with a visible infestation or sooty mold infection, be sure to target those areas.
When to Avoid Using Neem Oil
There are two times when you will want to avoid using neem oil on your citrus trees.
The first case is when the tree is close to a beehive.
Droplets from neem sprays can become airborne by the wind and potentially contaminate the hive.
The second instance is when the tree is close to a water feature.
Neem oil is safe for use around humans and pets but is been found to be mildly toxic to some forms of aquatic life.
Applying neem too close to an inhabited body of water can lead to contamination and should be avoided.