Has my tree got Citrus Leafminer?
What is Citrus Leafminer?
At the beginning of summer, silvery thread-like snaking tunnels often appear on new growth on the tips of citrus trees. By the time we see it, it is too late to do anything about it, other than to prune off the tips. The citrus leafminer is the larvae of a silvery moth that is about 4mm in length, and true to its name, having laid eggs on the leaves, it ‘mines’ them for its food. It does this by burrowing into the leaf, leaving an unsightly trail of no regular pattern all over the surface. It causes significant damage in summer and autumn but is many generational per year and can do damage at any time. You are unlikely to see the moth as it only flies at night.
How to treat Citrus Leafminer
The best treatment is white oil which can be made at home. The oil smothers the eggs preventing the larvae from hatching. Spray both sides of the leaf. It is best to start spraying mid-spring to be sure of being ahead of the leafminer’s egg laying schedule. This is particularly important for young trees which can be set back by severe attacks.
To prevent citrus trees developing soft, new growth in summer, avoid using high nitrogen fertilizer in August. (Fertilizer is generally applied in March and August – see article in July newsletter). *See below for a list of high nitrogen fertilisers.
Homemade white oil recipe
1 cup cooking oil
1/4 cup detergent
- Place in a bottle and shake and it will turn white.
- Label it the bottle with dilution of 1 tablespoon per litre of water.
- Spray on both sides of citrus leaves in this dilution.
- Repeat spray treatment every 7 – 14 days until the end of summer.
(White oil is also effective for mealy bug, aphid and scale).
*High Nitrogen Fertilisers include solid poultry manure, liquid manure, fertilisers containing urea and ammonium sulphate, feathers, blood, bone meal, and blood and bone.
Written by Robin Gale-Baker.
Read more citrus articles on our blog.