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Citrus such as lemon and lime trees are hardy and easy to grow. But citrus can be vulnerable to pests, diseases and environmental stress.
This guide will help you identify common problems affecting your citrus and what steps to revive the tree.
How to control common citrus tree pests
Citrus trees are often impacted by pests that can harm both the tree and its fruit. Pest infestations left unchecked can cause long-term damage.
A very common pest is the citrus leaf miner, a small larva that causes curled, distorted leaves with silvery trails inside. If you spot these trails, prune the affected leaves and treat the tree with horticultural oils or neem oil to control the infestation.
Another pest to watch for is the citrus gall wasp, which causes swollen, woody galls on the stems and branches. If you notice these galls, prune the affected branches in late winter and dispose of them properly to prevent reinfestation. Placing traps around the plants can prevent infestation.
Fruit flies can also damage your citrus tree by causing small puncture marks on the fruit. These marks lead to internal damage and reduced fruit quality. To manage fruit flies, place fruit fly traps around the tree and cover the fruit with mesh bags to protect it.
Aphids, tiny insects that cause leaf curling and leave behind sticky honeydew, are another pest to monitor. You can control aphids with insecticidal soap or by introducing natural predators like ladybirds to the tree.
Mealy bugs and scale insects, which appear as white, cottony clusters or hard, shell-like bumps on your tree, are also common citrus pests. These insects suck sap and weaken the tree. You can treat them by applying insecticidal soap or manually removing them.
How to treat citrus trees with fungal diseases
Citrus trees can be susceptible to a variety of fungal diseases that can reduce fruit quality and yield. One such disease is black spot, which causes dark spots with yellow halos on leaves and fruit. This leads to premature leaf drop. To manage black spot, prune the affected areas and apply copper-based fungicides to control its spread.
Citrus scab creates raised, corky lesions on both leaves and fruit, causing the fruit to distort and crack. To manage citrus scab, use fungicidal sprays and prune the infected branches.
Another common fungal issue is anthracnose, which leads to dark lesions on fruit and twigs. It can cause leaf drop and twig dieback. Improving air circulation around the tree and applying copper-based fungicides will help control anthracnose.
Phytophthora root rot affects the roots of citrus trees, leading to yellowing leaves, wilting, and decaying roots. This makes it difficult for the tree to absorb water. To treat root rot, improve soil drainage and avoid overwatering.
Collar rot, often caused by waterlogged soil, appears as brown, rotting bark at the base of the tree. To manage collar rot, keep the base of the tree dry and apply fungicides as needed.
How to fix citrus nutrient deficiencies
Nutrient imbalances can affect citrus trees, leading to poor growth, yellowing leaves, and decreased fruit production.
A calcium deficiency can cause fruit cracking. To address this, add lime or gypsum to the soil to improve calcium levels.
Iron deficiency causes the leaves to yellow while the veins remain green. Apply iron chelates or a foliar spray containing iron to resolve this issue.
Magnesium deficiency leads to yellowing between the leaf veins. To remedy this, add Epsom salt (magnesium sulphate) to the soil.
Manganese deficiency causes poor growth and pale new growth. Apply manganese sulphate to the soil to provide the tree with the necessary nutrients.
Nitrogen deficiency results in pale, stunted leaves and poor growth. Use a nitrogen-rich fertiliser to support the tree’s growth.
How to promote citrus health
Potassium, especially in the form of sulphate of potash, is essential for healthy citrus trees. It aids in flowering, fruit quality, and disease resistance. Apply potash in early spring and late summer.
Using a balanced citrus fertiliser will also promote healthy growth and fruit production.
How to revive a sick citrus tree
After identifying the issue with your citrus tree, follow these steps to help it recover.
Start by pruning any dead or severely damaged branches. This will encourage healthy new growth and improve air circulation around the tree. You can prune at any time of the year.
Water your tree deeply, ensuring the soil dries out slightly between waterings. Avoid waterlogging, as citrus trees do not tolerate wet feet.
Fertilise your tree with a balanced citrus fertiliser, following the manufacturer’s recommended application rates. Overfeeding can harm the tree, so it’s important to apply the right amount.
If your tree is suffering from root rot, improving soil drainage is crucial. You may need to amend the soil with organic matter or even repot the tree to enhance drainage.
Regularly inspect your tree for signs of pests, diseases, or nutrient deficiencies. Early intervention is essential for maintaining tree health and ensuring a good harvest.
Keeping safe when treating your citrus tree
When applying insecticides or fungicides to your citrus tree, it’s important to wear the proper personal protective equipment (PPE) to ensure your safety.
Essential PPE includes chemical-resistant gloves, long sleeves, long trousers, and closed-toe shoes to avoid skin contact. Safety goggles or a face shield will protect your eyes, while a respirator or mask will help you avoid inhaling harmful particles. A hat or hood is also recommended to protect your head and hair.
More help for your garden
Check out the guide How to diagnose a sick plant for more information on identifying and treating various plant issues to keep your garden healthy.
The Bunnings Workshop community is also here to help if you need more help with your citrus. Don’t hesitate to ask a question.
