Regardless of how we grow citrus trees, they can easily be susceptible to attack by citrus leaf miner. Not only is citrus leaf miner damage unsightly, but if it is not prevented or treated promptly, it can cause damage to citrus trees, including a reduction of fruits. So without resorting to harsh chemicals, let’s look at ways to control citrus leaf miner naturally and organically so your citrus trees stay healthy and thrive.
What is Citrus Leaf Miner?
Let’s start by identifying the citrus leaf miner (Phyllocnistis citrella). The citrus leaf miner adult is a very small, silvery-white moth, who flies at night, with a wingspan of just .3 inches (5mm). They lay tiny eggs on the underside of new leaves, and the little larvae hatch and burrow into the soft new leaves. So it is not the adult moth who causes the citrus leaf damage but the larvae.
The consequential damage caused by citrus leaf miner as they tunnel through the leaves, eating their way as they go looks like wobbly silver lines or little blisters on the leaves. Hence the name “Leaf Miner”. Gradually the leaves also become distorted and curl up when the larvae begin to pupate.
The mature citrus leaf miner larvae are yellowy-green tiny worms, and they are a warm-weather pest so they are most active from mid-summer through to autumn.
Each citrus leaf miner life cycle is relatively short at only 2-3 weeks but there are many generations throughout the season.
Citrus Leaf Miners are particularly attracted to small young trees, potted citrus plants and new leaf growth on mature citrus trees. The new leaf growth is particularly attractive because it’s soft and apparently delicious to citrus leaf miners!
Any damage citrus leaf miner cause to larger established citrus trees can be comparatively harmless, but they do still cause problems for the tree and allow disease to infect the plant via the damaged leaves. And they are a frequent cause for lower fruit yields.
Plants Attacked by Citrus Leaf Miner
Younger citrus trees and those grown in containers are particularly at risk; the citrus leaf miner can stunt growth. And if the attack is severe, they can even cause young citrus trees to die, particularly those that don’t have mature leaves to enable them to photosynthesis.
Traditional Chemical Treatments for Citrus Leaf Miner
Traditional treatment for citrus leaf miner often involves a pesticide spray. The spraying must be done at the right time to be effective. Too early or too late, and the pesticide does not impact the larvae or the moths. The ideal time to spray is in the spring once a day for a week.
However, this treatment is hit and miss, and if you want to go the chemical route, then a systemic treatment that is applied to the soil so that the citrus tree takes it up internally can stop infestations.
As home gardeners, we can choose to avoid chemical treatments and use a more natural and organic approach to treat citrus leaf miner.
Lacewings and Parasitic Wasps to Treat Citrus Leaf Miner
Natural predators can be encouraged into the garden to help control citrus leaf miner. They include lacewings and parasitic wasps. They do tend to need our help to find the leaf miners. Hosing any dust from the citrus leaves helps them find the problem.
And growing mint, carrot and aster family plants (including daisies, marigolds and zinnias) nearby attracts the beneficial parasitic wasps and lacewings.
Organic Treatments for Citrus Leaf Miner
Spraying citrus trees once a week during the spring with a natural organic pesticide derived from plants is the simplest method. By using neem oil which is derived from the Neem tree, there’s the benefit of being environmentally friendly too. Most neem oil spray treatments work by preventing the adults from laying their eggs.
You can purchase a ready to use Neem Oil spray or make up your own spray – see recipe further along.
When using this method, start in the early spring and pay particular attention to the underside of young leaves. Both the underside and upper side should be sprayed until they look saturated. Most neem products should be reapplied after heavy rain and about once a week during the leaf growing season.
Just Spotted Citrus Leaf Miner Damage?
Fortunately, if you have just spotted a problem, there are also neem-based products that penetrate into the leaves to kill the young leaf miner larvae. These products are generally reapplied every five to fourteen days the whole time there is new leaf growth.
Prevention of Citrus Leaf Miner
The adults seek out new growth because the leaves are soft and larvae find it challenging to tunnel through mature leaf growth. Therefore attacks can partially be avoided by only pruning once a year to minimize new growth. Removing any suckers promptly also helps.
Clearing Up to Control Citrus Leaf Miner
Whichever method you use and I strongly favour a neem oil product for a natural solution, it is important to be vigilant and to use good housekeeping, or should I say plant keeping?! practices.
Do this by removing and destroying any citrus leaf miner damaged leaves or fallen leaves. Some growers suggest leaving treated leaves on the trees to help sustain the tree, but I only recommend doing so if you are confident that you have effectively treated the problem. Caution is suggested if a tree has had a large infestation not to remove all the leaves, which could be fatal to the tree.
DIY White Oil for Citrus Leaf Miner
You can make up your own white oil to manage citrus leaf miner with ingredients you already have. Simply use:
1 cup of vegetable oil
1 teaspoon of mild dish liquid detergent
Dilute this in water at a ratio of 40 to 1. For example, 1 quart (1 litre) of water to approx 0.8 oz (25ml) of vegetable oil and detergent mixture. Mix and spray your citrus trees in the morning to avoid the oil causing sun damage to your trees.
Remember, this oil does not kill the citrus leave miner, though it does stop them from laying their eggs. So you should still go ahead and remove visible leaf damage.
How to Make Up Neem Oil Treatment Spray for Citrus Leaf Miner
Neem oil is made from the fruits and seeds and sometimes a few leaves from the neem tree. It is an effective natural insecticide that is not harmful to us or our pets.
Using neem oil as a preventative works because the citrus leaf miner does not like the smell of the oil and because the oil solution makes the leaves slippery for them.
By making your own treatment, you control the potency and by making small batches for individual purposes you avoid the shelf full of part used treatments. You can purchase horticultural neem oil here.
For citrus leaf miner control you need:
1.5 teaspoons neem oil
1/2 teaspoon mild dish liquid soap
1 quart (litre) of water
Simply add the water into a spray bottle, add the neem oil and liquid soap and give it a mix.
For best results use the same day it is made up and shake well before use.
Again, this treatment won’t kill the citrus leaf miner, but it will deter them from laying their eggs. So remember to remove the leaves from the citrus leaf miner damage when you see it.
By enjoying citrus trees in our garden, we are likely to experience citrus leaf miner at some point. Taking preventative steps will go a long way to protecting your citrus trees and keeping them healthy. By being vigilant at checking the undersides of leaves, particularly at times of new growth and keeping a supply of suitable natural and organic products, we can minimize the damage caused to the health of the citrus trees in our yards and enjoy the resulting fruits.
Reusable Glass Spray Bottle – plastic or glass bottles can be used.
Plastic Spray Bottle – As above, either plastic or glass spray bottles can be used.