Have you noticed strange silvery squiggly lines on your citrus leaves? It’s probably citrus leafminer damage. Find out how to treat citrus leafminer without chemicals. Keep your lemons, limes, oranges and other citrus trees healthy with these practical tips.
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What is citrus leafminer?
The adult citrus leafminer (or citrus leaf miner) (Phyllocnistis citrella) is a type of moth. Originally from South East Asia, this pest is now found in many citrus growing regions including Australia and Florida.
This tiny moth flies at night and lays its eggs on young citrus leaves, usually on the underside. When the eggs hatch, the tiny larvae grubs eat the leaves, leaving characteristic silvery tracks. These squiggly tunnels or ‘mines’ are how this pest gets its name.
The moths themselves are tiny, only about 5mm (less than 1/4 inch) long. Adult moths live for around a week and a female moth can lay about 5o eggs in that time. The eggs and the larvae are hard to see as they are so small.
Citrus leafminer infestations are more common in later summer and early Autumn. The time from laying eggs to the larve maturing takes about 2 to 3 weeks.
Types of citrus affected by citrus leafminer
Leafminer affects all types of citrus. This includes commonly grown trees like lemon, lime, orange, manadrine and grapefruit. It also affects native citrus varieties, like the Australian native finger lime. It doesn’t matter if they are potted citrus or garden trees.
Citrus leafminers are more common on new leaves and on younger, less established citrus trees. In my garden, fortunately only one of my potted mandarin trees has ever been affected by citrus leaf miner pests.
How can I tell if my citrus tree is affected by leafminer?
It’s too hard to see the tiny eggs or larvae of citrus leafminers as they are so small. You are most likely to notice citrus leafminers once you see the damage, usually the silvery or white wiggly lines on your citrus leaves. Other signs are curled, twisted leaves. This is because the larvae curl leaves around themselves for protection as they mature.
Should you treat citrus leaf miner?
If you find citrus leaf miner tracks on your citrus trees, don’t panic. These pests are not going to kill your tree. However, because the larvae cause damage to the leaves, this affects the tree’s overall health by affecting photosynthesis.
Your trees will still produce fruit, but not as much. Trees can also be stunted and not grow as well. An unhealthy tree can also be more vulnerable to other citrus pests.
Trees affected by citrus leafminer can also have badly distorted leaves, which doesn’t look very attractive either.
How to treat citrus leafminer
Fortunately there are a few easy ways to treat citrus leafminers that don’t involve heavy chemical insecticides.
Start by physically removing pests
Before you treat your citrus tree, make sure to remove any leaves with obvious signs of citrus leafminer. Place the leaves in a plastic bag in the sun for a few days to ensure the larvae are dead before disposing of. Don’t put the leaves in your compost, because you don’t want more eggs to hatch or the larvae to mature.
Avoid using insecticide sprays if possible
If you do decide to treat your trees with a spray for citrus leafminer, please think carefully about using an insecticide. You might end up killing the good insects that help keep your tree healthy. Predatory wasps and lacewings are natural predators of citrus leafminer, and other pests so you want to keep these around. These helpful insects can be the best natural remedy for citrus leafminer.
If you need to spray
If you have a more severe infestation, you can choose to spray with a horticultural oil. Be aware that this can still affect the beneficial insects too. Using a citrus spray containing natural pyrethrum mixed with canola oil can be effective. It’s still an insecticide, but is at least a little less toxic than some other options and is suitable for organic gardening.
Make sure to spray your citrus trees in the early morning to minimise harm to beneficial insects. Don’t spray when the weather is too hot, windy or when it’s going to rain.
Disclaimer: These notes about spraying are for general information only. If you have any questions about whether a product is suitable for your needs, speak to your local garden centre or contact the manufacturer. Please also make sure to read and carefully follow any instructions on the labels of citrus pest sprays.
Try a homemade alternative to chemical sprays
A great alternative to buying a spray for citrus leaf miner is to make your own at home. Simply mix together:
- half a cup of vegetable oil;
- half a Tablespoon of dishwashing liquid detergent;
- 5 litres of water.
Homemade oil spray won’t kill citrus leafminer, but instead acts as a deterrent to the moth laying more eggs on your tree, This is why it’s important to remove the affected leaves first.
Prevention is better than cure
Although a common problem, you can help protect your citrus from leafminers by keeping them healthy. Weak or unhealthy citrus trees are more prone to attack from pests like citrus leafminer. Look after your citrus trees well by feeding and watering regularly. This will help to keep pests at bay and avoid the need to use any sprays, even organic ones.
References and more information
For more information about citrus leafminre, see the following references we’ve referred to in this post:
- NSW Department of Primary Industries factsheet, Citrus leafminer.
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